Bug 856085 - [sms] support multiple term search highlight r=julienw

https://bugzilla.mozilla.org/show_bug.cgi?id=856085

-  Remove apps/sms/js/search_utils.js …  c1e5b61
-  Implement Utils.Template API …  8207244
-  Safe template string interpolation. …   a768e01
-  Utils.Template refactor …   01f119d
-  Update Utils.Template uses; fix naming mixups; revert img src change …  9a49367
-  Break up escaping and formatting tasks …  118d456
  - Utils.escapeHTML now only escapes HTML
  - Utils.Message.format escapes HTML and applies special message display formatting
  - Utils.escapeRegex is used to make user input safe for regex construction
-  Utils.escapeRegex tests …   4d0e0cc
-  Safe user input tests (Fixes issue with special chars in user input, eg. "+") …   25dceec

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>