Small improvements collected in the last weeks, for
review in one go, but possibly to be split up in commits,
also some for master and some for 5.1.

• turn newclass.ui & testcases.ui into QFormLayout + fix bad automatic tab order in testcases.ui + "Inheritance:" label now properly aligned with lineedit + remove unneeded extra layout layers
• workaround for broken focus handling in KEditListWidget on "Add" button clicks or "Remove" with last item
• use generic "generated content" instead of "new class" in pages which are also used for non-class templates
• use i18np instead of static "Output file(s)" on output page
• use ICore::self()->projectController()->projectsBaseDirectory() as fallback starting folder, not QDir::homePath()
• add a placeholder text to class identifier lineedit which hints that namespace can be entered there as well (was not obvious to me :) )