Merge pull request #56 from apdavison/master

Assorted minor fixes; added some built-in dimensions and units to Python library
Added equals magic method for Unit and Dimension
Added check for matching dimensions
debugged dimension checking on properties and added unit test
added missing file for unit test
added uncertml examples to repository
removed comments
imported built-in random distributions from uncertml
moved parameters above RandomDistribution tag in randomdistribution
catalog of built-in random distributions
added missing parameters to binomial distributions
implemented reader/writer for RandomDistribution class
Updated random distribution format to match that agreed upon in Antwerp
Implemented RandomDistribution reader and writer plus unittest
Merge remote-tracking branch 'upstream/master' into random_distributions

Conflicts:
	lib9ml/python/nineml/abstraction_layer/dynamics/writers/xml_writer.py
	lib9ml/python/nineml/abstraction_layer/units.py
refactored builtin -> standardlibrary
refactored BuiltIn to StandardLibrary
fixed bug in unit equality check and random distribution xml reader
fixed bug in unit-test replacing reference to local file with
tempfile.TemporaryFile
renamed PopulationSelection to Selection
implemented new projection syntax (and moved some old CSA files into
_old_projection sub-directory)