Added new ENABLE_XXX_FILTERING keys, code factorization in 1dinterpolations and new option for decimal dates in CSV plugin

Cf. issue 873

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...

Merge "file selector" changes

Also a logic change: The Number panel does not allow free text
anymore, i. e. if something is entered it _must_ be an expression (at
least for the warning to go away).
An exception are plain numbers, also possible in scientific notation.

I. e.:
2+2 <-- not ok
text <-- not ok
${{2+2}} <-- OK
${env:VAR} <-- OK
123 <-- OK
10e-3 <-- OK
(empty) <-- OK

This should fix issue 872 where mounted shares are not visible on Mac

This worked when the help file was its own "application" in the main
GUI. Would be no problem to generalize, but "for the moment" just note it
like this.

This way, if a "validate=..." property is set in the XML, this has
priority and the warning triangle is shown if coordinates are entered
(which do not fit the user specified regex).

No more "invisible" link, added tooltips

Now we have small icons to make things clearer

... to prepare having "valid" icon

Also switch warning colors

There was some messed up code left from when it was only frames we could
highlight. Much better now.

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.

- No need to refresh apps anymore
- change link syntax from help:// to doc://
- add link to help from settings page
- some comments

Now our main menu items all have icons and are discerned from
items macOS adds automatically.
Slightly more stringent naming.

This gets rid of an inconsistency where on macOS CMD+H was
already reserved for hiding the window. It's nicer anyway
and we get rid of an almost empty menu ("window").

Now we focus on the styling widget (usually the label), to scroll to the
beginning of the content.
(Otherwise the horizontal scroll bar would center)
Also: use the same color for frame and panel highlighting.

There were still crashes where a Timer was called on an invalidated
object. Now, this timer is in Atomic and therefore gets destroyed with
the widget.
This way we can have multiple stylings running and it is more logical,
cleaner, and more general purpose.

... of the main windows in place (unless of course the settings are
reset).

Clicking "reset" in the Settings window should now behave the same as if
the settings file was deleted manually before starting, i. e. restore
all defaults immediately.

For the styling timer we can not use the static version of singleShot,
because we must be able to stop it (when switching XMLs while something
is being highlighted).
Also, an INIParser object has been leaking

Now the user can choose to restart INIshell immediately if any of the
appearance settings have been modified when saving.

This layout should be well known and unsurprising to users, and the
ability to just cancel if something was changed by accident is also
nice.
Also, all windows now have reasonable minimum sizes.

Maybe something like this should also be done when saving...

Otherwise, window size settings etc. would be saved as-is on the next
program quit, making clearing these automatic position settings not
very effective (would have to go through command line args).

Namely "open parent folder" and "delete file"

This feature has been broken with a commit in April... now it should
work again.
I. e.: If unknown keys are read in, they will be shown (and highlighted
as invalid) in the Preview Editor and also saved back out to the file
system.