Refactor sitebase to accept level, message

level can be "danger", "success", or "info" (which are red, green, blue,
respectively)

Fixes #306
Remove unnecessary parameter from MainHandler

analyses was being passed, but is not necessary. @squirrelo agrees that this
is probably just a vestige of a more ignorant time... :)
Use new messaging system for study creation

Message is displayed on successful study creation
Add message+level to MainHandler
Assume message+level exist on index.html

rather than checking to see if they exist
Revert "Assume message+level exist on index.html"

This reverts commit 9f3968308d997ddee9efcf7cc98946f1e4cc21ba.
Merge pull request #529 from adamrp/sitebase_messages-issue-306

Add level and message to sitebase (issue 306)