Bug 845173 - [MMS][Utility] smil document generate and attchment extract utility for MMS message - r=julienw

Implements a parser and generator for SMIL XML format, the format used by gecko for MMS, which is converted to/from arrays for consuming in the sms application.

Co-Authored by @steveck-chung and @gnarf37
Merge pull request #9410 from gnarf37/845173

Bug 845173 - [MMS][Utility] Convert HTML element to mms SMIL and vise versa. r=julien