Story 1604: Remember mobile thanks

If the user has already been thanked, make the button greyed out
and display the text "Thanked" instead of "Thank".

Dependency: Ife9f456a7a9cf74b1b54fdc6128feb230fd6f671
Bug: 59828
Change-Id: Ifab78fe62910c9c3f2a927a6a4bbe28fb953b160
Merge "Story 1604: Remember mobile thanks"