Make / db names work in windows

Problem - Couchbase replaces "/" characters in DB names with ":" characters. But ":" characters are illegal in Windows!

Proposed Solution - Use "!" character instead of ":" character

Justification - http://docs.couchdb.org/en/latest/api/database/common.html in the section on PUT 
/{db} defines the legal letters in a CouchDB db name. http://en.wikipedia.org/wiki/File_name#Reserved_characters_and_words identifies characters that are problematic in various file systems. Notice that ':' is listed. A character that is in neither list '!'. I actually did test it in Linux, OS/X, Windows 8 and Android KitKat and it worked just fine.

Problem with Solution - Any existing DBs that used '/' will stop working with this change since they won't be found. :(