MidiPlayer: style overhaul
MidiPlayer: Update copyright headers

Add Haiku, Inc. for all changes 2008-2014 based on commit logs.
If people want to assign their own copyright for work they did they
probably should add there name to the copyright list.
MidiPlayer: Update version to 1.0.1 final

Change the BAlert about box into a BAboutWindow.
Add Authors based on commit logs.

Unfortunately the description contained:
"Haiku MIDI Player 1.0.0 beta\n\n" which means that it
is going to get flagged for re-translation, sorry! This was
bound to happen when the version number changed,
on the bright side it shouldn't happen again in the future
since the Name and version number are separate.
MidiPlayer: update readme.html
MidiPlayer: Rework layout

#9882 comment:8 suggested applying a similar fix
to MidiPlayer as the one to Backgrounds, which makes
the menu fields variable width and isn't affected by the
check box.

In addition this replaces BGroupLayoutBuilder and
BGridLayoutBuilder with BLayoutBuilder templates and
replaces hardcoded spacing units with B_USE_ spacing
constants.

I also put the Volume slider on its own line and tightened
up the spacing around the scope view.

picture:
http://31.media.tumblr.com/74d93b806033d9adee83eeb2adead48d/tumblr_n7v06onPdl1r0f0hfo1_250.png