Contacts: allow theming via theme chooser

Change-Id: Iddd6874ed420611a98d64aadede0bb203a707f2b
Fix conflicts after merge upstream/cm-10.2:

Conflicts:

res/layout/editor_account_header.xml
res/layout/editor_account_header_with_dropdown.xml
res/values/colors.xml

Change-Id: Icecf28e4a0acd1fda92405029d2997b39e609352