Fixes: Introduce a cpp settingspage containing file naming conventions (lower case and suffixes). Reorder VCS settings pages.

Task: 241959, 248085

RevBy: Optics/Naming checked by con
Details: Give IOptionPage an id() to differentiate from trName(). Make showOptionsDialog return a bool (applied) and give it an optional parent. Change Cpp and form class wizards, give them a Configure... button to change those settings.

Task:     - 244529
Details:  - It just doesn't work in Mac menus (at least not with Qt, but
I suspect it's some Mac thingy), so just don't do it.

Task:     -
RevBy:    Thorbjorn
AutoTest: -

in place
RevBy:   con

RevBy:    andre
Details:  - the settings have not been taken into respect so far.

    Task:     180315
    RevBy:
    Details:

    Details:  also accept trailing slashes

Many singletons have their own instance() method, in which case there is
no need to use ICore::instance() to get access to them.

replace ExtensionSystem::PluginManager::instance()->getObject<Core::ICore>() by Core::ICore::instance()

forward declaration is sufficient.

Details:  - Naming convention

Details:  - Conform to naming convention

The previous interface wasn't sufficient to properly support the Apply
button, since it didn't separate applying the changes from the cleanup
phase.

Designer settings pages still need some fixing.

Fixes Apply button causing problems for certain plugins, for example the
QuickOpen.

Details:  - To make it conform to naming convention.

Details:  in all pluginspecs.