Miscellaneous improvements for Launcher UI:
- Implemented "show intro" toggle in settings
- Install/Update/Enable buttons are now visible even when mod info is hidden
- Fixed behaviour of show mod info switch, added more obvious button to enable it
- Removed no longer used "Enable mods on install" switch
- Added buttons to open data, user data and temporary directories
Fixes 1856 - Griffin Bastion will be behind Town Hall
Fixes 1852 - fixed typo in tower config and added check to detect such cases
Updated changelog
- migrated boost::function/ref/bind to std:: variants
- added all SDL2 directories to CMake (in case if any SDL2 module is installed somewhere else)
- fixed Clang compiler warnings
- fixed casting sacrifice spell (was broken and now fixed partially)
First part of fix for 1712
 - implemented recursive search for missing dependencies
 - todo - update GUI. As of now Gui may provide incorrect information
Fixed rendering of bitmap fonts shadow
Proper fix for #1712 - Building requirement tests are now fixed
- added minimize() method in logical expressions that will remove excessive elements
- replaced forEach() with morph() that allows replacing types in variant
Possible fix for neutral palette (1867)
Merge remote-tracking branch 'upstream/develop' into develop
 Minor fixes and cleanup