Display manage conference button.

The manage conference button allows the user to unmerge or hangup one of
the calls in the conference for GMS and IMS devices.
+ Move the original manage_conference_call_button layout file to
layout-h600dp and layout-w600dp-land directories.
+ Fix the button to the bottom of the call card fragment.
+ Split the "manage conference call" text into two pieces and put
"conference call" on one side and "manage" with the icon on the other.

Bug: 26253432
Change-Id: I9853f479d4e45591026fe7a753eca1ef69b00e42