bfGetPlane fix and hardcoded version removal

The local merge of #627 into the daily merge build exposed an obvious bug in bfGetPlane() (which required the version number to be >= 5.0 to show up). This PR:

- removes the hardcoded version check from `bfGetPlane()`
- fixes the call to `makeDataArray2D` for signed pixelTypes
- add additional validator to the input check as well as corresponding unit tests

As an outcome of this PR, [BIOFORMATS-merge-matlab-develop](http://hudson.openmicroscopy.org.uk/job/BIOFORMATS-merge-matlab-develop/) is expected to turn green again.