Units metadata panel

In the Metadata Forms, I'm putting the Value in the field and the Unit in brackets (see screenshot). Units are displayed "as is" but need converting from CAPS to lowercase in a future PR.

To test, use list of units at https://github.com/will-moore/openmicroscopy/commit/2a1ab71115f948bae9bd911fa9f751906ee7b44a and if they are displayed in the Acquisition panel in web then they should have units shown.

A couple of attributes are in 'Settings', E.g. Wavelength (LightSourceSettings) and Voltage, ReadOutRate (DetectorSettings) as well as in the object itself (LightSource or Detector) so these need to be checked under Microscope tab as well as Image / Channel.

Pixel Size, DeltaT & ExposureTime and Channel Excitation/Emission wavelength will be handled in another PR since they will require changes in Blitz Gateway.

![screen shot 2014-11-25 at 00 19 30](https://cloud.githubusercontent.com/assets/900055/5175923/54e80732-7439-11e4-88c0-1160bbbdf751.png)

--no-rebase