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").

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

If an unknown section is encountered, check our list of dynamic sections
if it fits and should be created.

Since the tab index will change when removing other tabs, the lambda now
emits the tab name to look for and delete.

This implies having a clear parent Section with a "+", and the
duplicated templates can be removed with a "-".

Revert to idea of using a global container - it would be possible to do
it without and always search on the fly, but readability would suffer...

Now dedicated <section> tags may be flagged as templates, and the
respective tabs will show a custom button to take some action to be
implemented.

Add possibility to show the user guide with a specified tab opened. Use this to link to the Preview section from the preview menu.

The color scheme has been redesigned and now follows Solarized (https://en.wikipedia.org/wiki/Solarized_(color_scheme)). Instead of directly coding colors in the code, they have all received symbolic names and then the names are mapped to a specific color. On the long term, we will be able to offer several color schemes, like Solarized, osX, Windows, etc

Because there was no way to completely reset a Numbers panel (there can't not be a number in a spin box) this is now possible via a generic context menu in all panels. Restructure the menu a little to make these functions more clear

page

Add a menu to show/hide the workflow panel in case it gets lost (it can
always be dragged but with the current icon this is not too obvious)

re-check on onPropertySet when the value does not actually change.

whole sections.

Formerly INI keys were changed live when changing the value through a
panel, eliminating the need to loop through the panels for output.
However, this introduced more and more intermediate loops (like
disabling child panels of Dropdown, Choice, ... that are not shown) and
gave some headaches when working with missing mandatory values and
similar things. Hence, now we keep the original INI values read from
file as they are and and do loop through the elements at the end to get
the user set values.
Also add a few toolbar buttons and minor changes here and there.

The selector panel is started, and to make this work without unwanted
side effects in very special cases we need to allow Qt to resize all
widgets in the scroll area. Manually calling the routines does not work
cleanly. At least, this also gets rid of the need to redraw the
scroll areas. Took a while to pinpoint this...
Additionally, for now the checkboxes can show/hide their silbling groups.

If the section is not available, use the (grand)parent's. Split section
from key and re-combine them to the object name (which we can search
for). Give the main, always present, groups a different ID. Transfer
QWidget inheritance from the elements to Atomic.

Split section from ids --> keys

transfer QWidget inheritance to Atomic

Set generic object name

give main group different id

Simple elements can be arbitrarly nested in groups. So far, the section
must fit the parent elements.

After a bit of a fight, we have a main tab bar that holds scroll areas
for each tab. Inside each tab is a group which can hold other widgets
and nested groups. The scroll bars control all nested groups, i. e. the
user can always scroll to the end of the biggest widget, no matter its
grouping level.

Elements of the same hirarchy will be grouped and layout-managed by this
class.