Readd main sheet

Which moves Adam's spells, to tabs in tabs. I will probbaly try to
restructure this stuff as well.
Start restructuring the source tree

Move MainSheet (CharacterSheet.qml) to its own directory,
ui/mainsheet. Currently uses aliases to mimick original structure
in the qrc file.

Will separate ui and logic properly later.
Readd the All Spells list

Still need to fix the filter though.