Enable original function version to be named

[jheintz]

@versionedfunction
def foo():
  return 0

@foo.version
def foo2():
    return 2

assert foo() == 2

versionContext[foo] = ??? #how do this? maybe <original> as magic string?
assert foo() == 0

[jheintz]

Enable string version context specification.

@versionedcontext(Foo.algo2) and @versionedcontext('Foo.algo2') and @versionedcontext({'Foo.algo':'2'}