fix handling of colorbars in R2014b

* E.g., testcase 96 `colorbarLabelTitle` failed due to the colorbar being filtered in R2014b
* The filter was extended to properly handle colorbars in R2014b
* Comments were updated a little bit

Issue https://github.com/matlab2tikz/matlab2tikz/issues/429 is related.
@PeterPablo I haven't tested the code but If you already adding the `'colorbar'` type to `m2t.cbarHandles` why are you keeping them in the relevant axes?