Added new mime types for JS and SQL

SQL uses the mime type application/sql on my system (Gnome 3.10.4 with
nemo), this did not exist so I created a symlink to text-x-sql.

JavaScript has the "official" mime type application/javascript (RFC
4329) now, so I moved it from text-x-javascript.svg to
application-javascript.svg and set up symlinks for
application/javascript, and text/javascript. Closes #170
Merge pull request #172 from RossBrunton/jssql

Added new mime types for JS and SQL