Changed the NITViewModel for simpler use

Used to be that it was an OmdbEntry and MovieWithGenres on the top level,
so I made it so that Movie/Genres/Boxarts are top level, instead of the
MwGVM
Added Tools.TraceLine

Wraps Trace.WriteLine but accepts string formatting. Will added the param
for option trace level or whatever.
Misc clean up and comments
Tweaked custom exception handling a bit

Maybe thinking that custom error handling is a bit tougher than I thought,
but hey, we're having fun right?