DllMacro.h ==> UiDllMacro.h
Lots of changes. Module search+load system is now working.
Moved module-related classes to src/calamares/modulesystem.
Fixes to startup code path.
Made ViewPlugins load into ViewManager.
Debug code: ViewManager currently only shows a plugin's prettyName.
Added ViewModule as a subclass of Module. Other kinds of plugins should
be supported in a similar way.