Bug 1041967 - [Messages] do some safe lazy load to improve launch latency

- Move scripts and css that not in the thread rendering call path into Lazyloader
- Add another callback for render thread while first panel is ready that we can lazyload/init the rest of part
- Prevent the body to receive any pointer events before all the UI modules init
looks like this make tests in sms_test.js fail :)

see https://tbpl.mozilla.org/?rev=aa17b79dcdc688e6bd5909f56b8369183472caa7&tree=Gaia-Try