Add Search Studies object

This object has natural language parsing for searches and returns a dictionary of {study_id: [samp1, samp2, ...]} of samples and studies matching the search query. An example query is also in the documentation, showing you can get pretty complex with them.
I don't think this actually does a substring match, see, e.g., [this article](http://www.postgresqltutorial.com/postgresql-like/).  If you want a true "includes" operator to behave in a way that the argument to "includes" must exact match any substring of the specified column, then it should be surrounded by percent signs (i.e., wildcard characters)
```python
return "%s LIKE '%%%s%%' % (self.term[0], self.term[2])
```