Select images on mousedown using Rangy

Removes _selectedImage.
Add test for unlinking image.
TridentPre7's _keyup: remove unused assignment
Image selection test.
Image selection test: assert only one node selected
Use `manipulationFunc` in image selection test
prepareUnitTestModule: support passing `options` on to the editor
Make jshint happy
manipulationTestHelper support click manipulations
Shorten long line
manipulationTestHelper support no manipulation
manipulationTestHelper: slightly more neat logic
manipulationTestHelper (and 2 more funcs) from test.js to utils.js
jQuery.fn.parentsOrSelf: was broken
toggleClass: toggle class of only the first parentOrSelf
Merge pull request #642 from wymeditor/prepareUnitTestModulePassOptions

prepareUnitTestModule passes options on to editor
Merge branch 'master' into manipulationTestHelperClick
manipulationTestHelper: semantic + minor logic changes
Move manipulationTestHelper to its own file
JSHint `latedef: nofunc` only on manipulationTestHelper