Send trackId instead of subtrackId.
Add object explanation to question types directives.
Add loader interaction between request of questions to the API.
Add validation to observable group.
*Add new UI validation over practice and question layout to make content editor HTML able to be shown to the user.
Remove old way to handle panels view.

*Need a way to keep the width of the question box to be maybe 75% of the available width. it seems very skinny right now.
Merge pull request #89 from joanrm20/master

Maua client fix and improvements.