Merge pull request #5 from heinermann/master

Asset file handling changes (round 2)
removed redundant logger dtor; streamwriter closes itself when GC'd
prep for importing brushes #1
JsonParser now static class, added basic error handling for JsonParser
more error handling, import brush dialog now shows
fixed asset loading thread starting before the asset directory path had been detected
removed redundant code
selecting a layer now lowers the opacity of all other layers in the part in graphical mode, rather than just displaying that layer
special brushes (connectors) can now have lowered opacity
removed transparency for tiles; stairs were too difficult to see
update gpl headers
rename dungeoneditor to starstructor
update folder structure
removed Editor namespace to avoid Editor.Editor shenanigans, moved everything from editor namespace to default namespace
use starstructor icon on all sub windows
comment editing, attribute changes, background darkening, merged from heinermann 9fc2cc0, 163f101, 0d8eaf4
added object tostring
add brush now lists all cached assets
now correctly redraws composite image when drawing with a layer selected
minor code cleanup