[1/2] InCall: Add a non-intrusive dialog for incoming calls

Change-Id: I7c8b5cc5138a5543be30579e99bd9989624e2abe
[3/3] InCallUI: allow disabling non intrusive incall ui

Change-Id: I86bd4b46f031004fa90f1d7936263f9dabcd3860
InCallUI: Disable Back button on Non-intursive InCall Card

Fix for jira issue http://jira.omnirom.org/browse/OMNI-296

PS2 to PS5: code cleanup

PS6: Remove Jira issue url from code

Change-Id: I257daccbb175265e2430f1b0b30c9175cb4b1981