Remove learning designer and producer openings from job page

Fixed install by adding mysql

More inputtype refactor …

- change a few comments / strings
- move extract_choices into the ChoiceGroup class

Fix alex vsepr 2 mitx

Fixed dependency problem introduced by MySQL-python by forcing distribute version >= 0.6.28 in pre-requirements

Added DEBIAN_FRONTEND=noninteractive to sudo apt-get which is required for silent mysql-server installation

Support blackout periods for restricting student forum posts per class

Implement basic ability to close off a forum for a given course such that Students can no longer post or edit, but can still view.

- small Attribute and InputTypeBase interface changes to make things cleaner
- move html quoting into templates (use ${blah | h} syntax)
- converting input types to use new format.

- add an Attribute class
- input types just need to declare which attributes they want, and how to transform and validate them, and the base class will do all the rest.
- change OptionInput to new format.

Feature/victor/inputtypes refactor

Add HD control to video player

Add google analytics to course info pages

Update Job Page with new positions

Allow optional advertised_start metadata in Course

Add MySQL-python to the requirements.

Allow optional advertised_start metadata in Course, to let people pre-launch thier courses quietly if desired.

Feature/victor/inputtypes refactor
- addressed comments and added a few TODOs.  Merging.