Usability improvements when editing cells containing xml or json

Hi Igor,
The only change is the last commit, by me:

(1) When editing xml or json, the "save" button has been renamed "mark for save".
(2) When you click on "mark for save", the button for actually saving modified rows to HBase is highlighted. Before, you had to click "mark for save", then click on a separate row, before you were allowed to actually save the changes.

Cheers,
-Matt Halverson