Bug 870416 - [MMS] Recipients container multiline view takes all available space

- When the screen resizes, generate a CSS rule that calculates the max available height
- Renames an existing element to match the naming convention
- Adds non-html interpolation support to the template matcher regexp
- Ensures that assimilations abide existing behavior rules

https://bugzilla.mozilla.org/show_bug.cgi?id=870416
Signed-off-by: Rick Waldron <waldron.rick@gmail.com>