Update selected databases page.

Closes #672 

Change "Selected databases" to "Selected article databases" in various places.
Add See also section to a couple databases.
Address accordion section styling issues.

#### Home page
![home-page](https://cloud.githubusercontent.com/assets/96776/4035969/4794009a-2c95-11e4-8edb-7ff36d11b7e3.png)

#### Databases masthead
![all-databases-masthead](https://cloud.githubusercontent.com/assets/96776/4035965/43fa1370-2c95-11e4-8b1f-6e54fbc75a03.png)

#### Selected databases page
![selected-databases](https://cloud.githubusercontent.com/assets/96776/4035968/4780a20c-2c95-11e4-80b5-bce2647b5acc.png)