add track height menu option to WiggleBase.js

Track height menu option adds a dialog that allows the track height
to be adjusted between 50 and 750.
add track height to menu bar

Track height can be adjusted per track or globally from the View drop
down menu.
add cookie to persist track styles
make getUserStyles and updateUserStyles methods in BlockBased.js to store persistent per-track style data using `browser.cookie`
tweak track height setting menu label, inline its callback
add units label to track height setting dialog
update release notes
Merge branch 'erbriones-master'
add an icon to the new vertical-resizing menu items