Addressed mhevery's comments from https://github.com/chirayuk/angular.js/commit/1b56c4c07848c1b1984138e3d65a10dae252faf9

- renamed $sce.makeTrusted to $sce.trust
- renamed $sce.isTrustedValue to $sce.isTrusted
- renamed $sce.getTrustedValue to $sce.getTrusted
- throw an exception instead of logging an error if attempting to
  $sce.getTrusted on an untrusted value
- used the global identity function instead of creating a duplicate
  local version