launching screen
launching screen examples working
example button is disabled if nothing selected
make checkbox working to show or hide launcher in launching screen
added option in preferences to show launcher again
dialog box closed after selecting option
#include<QSettings> added after #include<QApplication
QSettings header file added after QApplication
made the size of launching screen fixed
no launching screen if filename is given at cmd line
recents list in launching screen contains names of files instead of path
Merge remote-tracking branch 'origin/master' into launchingscreen
#894 compile fix for MDI mode, minor cleanup
#894 Minor cleanup
fixed open buttons in launching screen
minor code cleanup
Merge branch 'master' into launchingscreen

Conflicts:
	openscad.pro
	openscad.pro.user
	src/MainWindow.h
	src/Preferences.cc
	src/Preferences.h
	src/Preferences.ui
	src/mainwin.cc
	src/openscad.cc
Make welcome screen resizable and update some minor UI issues.

- Move images to icons folder
- Move "Show welcome screen" to advanced tab in preferences
- Set button styles via Qt stylesheet to handle hover and disable
- Rename config setting to "launcher/showOnStartup" and add default
Separate launching screen from main window and show before main window opens.
Add bigger logo image.