Add search by gene or transcript

[homonecloco]

If the user writes a transcript name, the search is by transcript. If the user search by a gene name, we get the added expression of all the transcripts.

This requires updating all the links. Now we have an explicit search_by field that resolves depending the type of search. If this parameter is setup, return the the corresponding transcript or gene according. If it is not set, search the best match for the query.

In the plots, the values are added on the server side, to avoid changing anything in the plot.

[homonecloco]

This also requires updating the results of the blast search, as the path is changed now.

[homonecloco]

The changes for this are added to master.
@Bijan-Ghasemi-Afshar, please merge back from master to your project. Once you do it, don't forget to do rake db:migrate. I added some indexes to improve the performance of the gene search.