selectively running unittest functions

[Daniel Davidson]

Here is a working solution: 
https://github.com/patefacio/d-help/blob/master/d-help/opmix/ut.d

Currently it only pulls in unittests at the module level. I'm 
sure it will work on unittests scoped to structs/classes, I just 
need to figure out how to determine if a compile time named 
object is an aggregate, as __traits(getUnitTests, foo) will 
complain if foo is not a module or aggregate.

With a source a.d and b.d like in: 
https://github.com/patefacio/d-help/blob/master/d-help/opmix/examples/ut/
it can pull out by module name and uda test name. It has a -s 
summary option as well.

Here is sample output: http://pastebin.com/fYd7k1Kz

Thanks
Dan