Web study search interface

This pull request is rather large, so sorry about that. It adds a ton of functionality to the study selection page, including the ability to search and select samples by metadata, select multiple data-types per study and multiple processed data files per data-type, and database updates for selection/deselection as well as the ability to continue selecting samples after leaving and then returning to the analysis pipeline. It also adds a dependency on the pyparsing module.

Currently I need people to play around with the page functionality and give input on what is broken/wonky, what needs to be changed interface-wise, and what needs to be added. 

Known issues:
 - ~~Use [chosen](http://harvesthq.github.io/chosen/) for the multi-select boxes for each data-type~~
 - Have some tooltip or other way of seeing the pertinent values for processed data
 - ~~Have some way of knowing what metadata categories are available to search over~~
 - ~~Add tornado tests once that package is figured out~~
 - ~~Handle malformed queries better than an error message coming up.~~
This won't really speed up anything due to how psycopg2 executemany operates. All the function does is create and execute one SQL call per tuple of items to send. This may actually be a bit better this way, as it sends the SQL in batches as opposed to all at once.