Bug 1053709 - Make SMS messages content UI RTL-friendly

- Mirror the incoming/outgoing message bubble layout
- Use  unicode-bidi: -moz-plaintext to display the content properly
plaintext didn't disable the bidi algorithm, it applied another level of bidi algorithm P2/P3 [1]. I provide another example for the ltr/rtl mix up. Not sure which kind of display sequence is the most appropriate for RTL user.

[1] http://www.unicode.org/reports/tr9/#P2