Made crowd server extensible to multiple crowds.
* Defined a generic interface (views, models, templates) for adding new crowds.
* Migrated the AMT crowd to the generic interface.
* Implemented an 'internal' crowd that runs tasks locally.
* Modified the scala http client to support multiple crowds.
* New README documenting the process of adding new crowds.
* Modified start/stop/post scripts to be more useful and run with multiple crowds.
* **Note**: requires upgrade of Django to run.