Add backend tests to check backgroundColor and siteLogo
# This is a combination of 2 commits.
# The first commit's message is:

Move rp_info.js to common/js/models.

# This is the 2nd commit message:

Use getter functions when accessing rpInfo
Cleanup of RpInfo related code

* Move rp_info.js to common/js/models.
* Use getter functions when accessing rpInfo
* create an instance of RpInfo in dialog.js instead of state.js