Include sample names & cancer type when searching projects from home page

[jluebeck]

E.g. searching "NCIH2170" returns nothing, but NCIH2170_LUNG is a sample in CCLE.

[jluebeck]

In views.py, this is all done in the gene_search function. We should refactor the code a bit so it is easier to work with, then add the ability to search by sample_name and cancer_type.

[jluebeck]

Add ability to go to "advanced search" as a link to the right of the home page search.

Alter home page search to default to searching for a sample, not a gene. Remove limit to classification from home.