Add Duration Columns to InfoTab

Duration for Spaces is updated automatically, but for descriptions the
value does not change since the audio file can not be edited at the
present time.
Chain Constructors to Reduce Redundancy

And also fix a bug with one constructor.
Remove Specific Column Widths in MainWindow

It seems that all these columns should have equal values. On top of
this, it appears that a column can be easily created accidentally by
clicking on the design window, which leaves me to believe this was auto
-generated.
Make first column fixed and others proportional
Add IsRecordedOver Property to Space

When set to true, it means that a description has been recorded in the
time space of that space.
Add a MultiDataTrigger to show space completness
Merge branch 'master' of github.com:IMDC/LiveDescribe-Desktop into valdev