This is issue 869 and is required for several reasons: 1) to make Inishell more
similar to MeteoIO, Snowpack, etc 2) because Qt6 is moving to CMake in
replacement of qmake 3) because it will "easily" allow creating native packages
for several platforms.

Now the PreviewEdit is properly parented and the garbage collector can
cascade down to the syntax highlighters (which are parented through
their text document).

- INI syntax highlighting moved from PreviewWindow to PreviewEdit
- Split up BSD code with separate header because most of it is actually
our own by now...

Cf. updated issue 872 for the problem this brings, but it should at
least be consistent

The name was a relict from the very first day of project structuring,
but this name here makes for much much nicer tab-completing to source
file names...

When this setting was split up from another one, one place was forgotten.

The menu just looks wrong without it... but now we avoid the problem of
CMD+Q by displaying the always available "ESC" shortcut.

This is now the same behaviour as for dynamic sections.

Before, it was tied to the "unsaved" warning when closing inis/XMLs,
but now the user can control this separately, hopefully encouraging
them to keep the more important ones.

We need this shortcut for the tabs, and this way CMD+Q quits the whole
application as is expected on mac.
We can still use this shortcut by repeating it until all tabs are closed
(and ESC also works).

This allows to still use ESC when a status message is displayed (like
"empty INI file") while keeping it working with the search text box

It was used to close the find bar but now just close them one after the
other... the Preview Editor was the only window this did not work for.

(Now the question remains how to handle Alt+F4 / CMD+Q --> on Mac it may
be expected to close everything?)

Now child windows' close entries are named better (close preview, close help)
and fit next to the main "quit inishell" menu.

Intermediate commit - to tune and to re-fix on other platforms

In addition to the command line --clear there is now a GUI button for
this.

...through keyboard shortcuts.

We need to be able to set the tab bar everything gets built into... so
first, split up some functionality.

Also duplicated headers plus better ordering

- The commanding lambda now correctly receives a constant index and
  therefore the correct tab name is changed.
- When previewing an INI file where all that has been done was to open
  an application without changing anything, it is now still marked as
  unsaved (because although it might save a click in special situations
  it does not make sense to have a different logic than in the GUI and
  can only be confusing).
- Default names now get an .ini file extension i. e. unsaved(1).ini.
- Path/filename splitting is done once on file changes and then reused
  from outside without asterisk shuffling.
- Minor logic cleanup, consts and styling

Files opened from the filesystem are now read only and not marked as
"modified". A tooltip listing the major shortcuts has been added. The
regex for coordinates has been improved (it is now the same as at the
other places in Inishell).

Otherwise, re-ordering of the variables declaration for better
alignment.

The drag & drop behaviour of the text editor itself is kept as-is
(moving text blocks with the mouse etc., and also inserting file names
if dropped into the text area) because we don't want to re-implement all
of this ourselves.
However, we display a guidance text if a user drags files over the text
area telling them where to drop them to open.

The virtual stations are given as "VSTATIONx", not "POSITIONx"!
Moreover, more links to the online documentation have been added and the
syntax highlighting (in the PreviewWindow) now supports the coordinates
specifications (otherwise, coordinates provided with ";" were shown as
comments).

better "unsaved changes" warning.

It should finally be relatively clear to the user what happens when an
INI is opened, and closed seemingly without changing anything - namely
that the application may have inserted mandatory keys.

The fonts are now setup in the constructor. An unnecessary script has
been deleted.

-Move setting to 'preview' XML section because it exists from another setting now
-Remove obsolete documentation
-Clear status on TerminalView clear ("Process terminated" etc.)
-Remove useless _ from regex (it is checked by \w)
-Extend INIParser unit test with *::EXCLUDE example key
-Cosmetics
(Might want to clear settings with ./inishell -ce)