Fixup reboot after install variables

* Create correctly named data manager variable 'tw_install_reboot'
* Make configurable through Settings
* Remove closing tag space in theme files (not personal preference,
  but should match surrounding code style)
* Fix the "two presses needed to enable" issue for the checkbox on the
  install screen

Change-Id: I0ceb60b4888a672e2f0ecb5672b03cc86615621a