Bugfix #1329. Fixed toggling the cell value in `checkbox` cells using ENTER key
Bugfix #1332. `source` function won't be invoked after clicking the arrow in cell of type `autocomplete`, if the cell is readOnly.
Added MultiMap, which is an extension of WeakMap. Besides using objects as keys, it enables using strings and numbers as keys
Bugfix #1320. Fixed translating property name to column index, if the property is a function.
Bugfix #1330. Autocomplete editor won't update choices list when mouse cursor leaves and enters the list.
Fixed major editor bug in editors which override beginEditing method. From now on, the decision whether to open and editor or not, depending on the readOnly property value, is made by editorManager, not the editor itself.
Bugfix #1362. Fixed determining an actual (in pixels) container height in IE8, when CSS defines height in percents.
Bugfix #1367. Fixed opening a cell editor using arrow in autocompleteRenederer, after the table has been destroyed and reinitialized.
Merge branch 'feature/bugfix-#1329' into develop
Merge branch 'feature/bugfix-#1320' into develop
Merge branch 'feature/bugfix-#1330' into develop
Merge branch 'feature/bugfix-#1332' into develop

Conflicts:
	test/jasmine/spec/editors/autocompleteEditorSpec.js
Merge branch 'feature/bugfix-#1367' into develop
Merge branch 'feature/bugfix-#1362' into develop
Fixed opening dateEditor mechanism, which was crashing tests in FireFox
Fixed MultiMap implementation, to work with IE8