getCellRenderer, getCellEditor, getCellValidator
Attempt to run cell menthod getters in IE - unsuccessful
Fixed modifying columns object while expanding type property.
Fixed demo/renderers_html with header menu
Merge branch 'feature/cellFunctionsGetters' into customHeaderRendererDemo

Conflicts:
	src/core.js
if method does not exist (eg. validator), returns undefined. TODO write test that overwriting type "numeric" with type "text" also overwrites numeric validator with undefined in cellProperties
fix demo in IE8, revalidate cells before render
numeric validator should validate null with the same empty string
Added spec helpers for new cell function getters
Fixed updateSettings tests
For performance reasons, cell functions getters can now take cellProperties object as the first argument. If cellProperties object is passed, then cell function getter won't call getCellMeta internaly, but will use this object instead.
Fixed manualColumnMove test
Merge branch 'feature/mergedCustomHeaderRendererCellFunctionsGetters' into develop