fix fxos_appgen package name.
Add support for configuring supported browsers through ini file.

This adds much more comprehensive support for ini files, and the ability to
override the ini file through command line arguments. It also adds the
ability to specify which products are supported through the [products]
section of the ini file. This provides a way of not requiring dependencies
for those products that won't be used in a given environment.
Start to use gaiatest for some Gaia UI functions when intereacting with B2G
Fix some small bugs
Fix command line parsing for mach integration.
Print a message about dependencies when installing.
Update the b2g browser support.
Remove an extra argument passed when requeuing tests
Ensure that the config path is set.
Remove an unneeded import
Fix config argument parsing.