Issue 301

Unify the console command lines between nunit-console and nunitlite.runner.  Also, add the --testlist option to allow for a file(s) consisting of a list of tests to run.

This is currently a one-way unification to make nunit.runner the same as nunit-console (and the corresponding tests).  The changes should be able to be backed into nunit-console with no affect, but I have left that for another PR once this is merged.

Probably, the common source files should be moved into Common when that is done.
From an object oriented POV, it seems to me that reading the testlist file in the command line processor is the correct place to read it.  It is only an alternative way of specifying the tests to the command line.  In fact, it can be used in addition to tests in the command line, and can be repeated as well.

The runner has no need (nor should it have one) to know where the list of tests it is to run comes from.