Allowing remote host for attachments

(cherry picked from commit aa258f23c77150befb2a8c0dfc239cd52ecb1877)
Setting longer TTL for tiles on /observations; allowing more filter options to use grid

(cherry picked from commit dd4d82af5263d3adb707608f3ff878768479e2ed)
Updated map3.js to send more parameters to windshaft; added underscore.js
Merge pull request #401 from pleary/master

Variable attachments_host; Longer tile TTL for /observations; More parameters can be send to Windshaft