Changed RowParser.load signature

Returns [Cue] instead of [GroupCue]
CsvParser.parseFromFile now uses "if let" syntax
Fixed CueComboBoxDataSource.

Replaced getSelectedWorkspace() with getSelectedCue()
Removed test code
Added CueQLabConnector

Appends Cues of any type to QLab workspace.
Added ViewController.selectedCsv field

Contains selected CSV URL.
Added "Append" button to append cues to QLab.
Fixed CueQLabConnector bug

Issue where appendCues didn't return if cues was empty.
Created GroupCueQLabConnector

Appends GroupCues to QLab workspace.
Changed sample CSV