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.

- all inputtypes should have id inputtype_${id}
- should have class capa_inputtype

- allows catching any exceptions and making sure the xml is in the error message
- isolates subclasses from external interface a bit

Remove non-working TrueFalse functionality from choicegroup, combine tests with radiogroup and checkboxgroup

Feature/arjun/allow save

Update startup script for 12.10 Ubuntu.

Added "quantal" to the list of known distribution names.

Improve fileinput message

Support for multiple rectangle hitboxes in imageresponse

 - switch to using registry
 - pull math and solution "input types" into a separate customrender.py file
 - make capa_problem use new custom renderers and input types registries
 - remove unused imports, methods, etc
 - add tests for math and solution tags.

- also add a test for chemicalequationinput

- tests
- rename it codeinput, with textbox still supported too