Fixed modifying columns object while expanding type property.
Fixed demo/renderers_html with header menu
Fixed an error in IE8, which occured when any value in dropdownEditor was clicked.
Two remaining $.contextMenu tests rewritten to test new, native contextMenu plugin.
Fixed highlighting matched phrases in autocompleteEditor
Fixed validation of Dropdown cell type.
Fixed validation of cells with allowInvalid set to false
Fixed showing selection fill handle in IE8
Changed editor API. val() has been split into getValue and setValue
Merge branch 'feature/dropdownEditorIE8Fix' into develop
Merge branch 'feature/contextMenuTests' into develop
Merge branch 'feature/autocompletePhraseHighlight' into develop
Merge branch 'feature/autocompleteCellValidation' into develop
Merge branch 'feature/borderFillHandleIE8Fix' into develop
Merge branch 'feature/valToGetValueSetValue' into develop
Merge branch 'feature/customHeaderRendererDemo' into develop

Conflicts:
	demo/renderers_html.html
	src/core.js
	test/jasmine/spec/Core_updateSpec.js
IE8 autocompleteEditor partial test fix.