First attempt at standardisation of names and parameter names for random distributions (relates to issues #282 and #296).
Forgot to add these files to last commit.
Changed random distribution parameters to kwargs.
Restored the option to specify parameters of random distributions as a tuple (as an alternative to the new option of specifying them as keyword arguments).

Also: added a maximum number of redraws for clipped distributions, updated the documentation.
Incorrect parameterisation of RandomDistributions is now detected at creation time.
Fixed some unit tests broken by previous commit.
Merge pull request #301 from apdavison/standard_random

Standardization of random distributions