[PATCH] new getDmDeps and getDmTarget functions

[Joel Granados Moreno <jgranado redhat com>]

Hey list:

Still think creating individual methons for each identification type is
overkill.  In other words I still prefer the getDmDeps(name=NAME) way
better.  I'd be convinced otherwise if there was another argument
besides just clarity.

I corrected some errors in the returning values and made sure that the
value contained in the maps was not none.  A little worried becuase if
map metadata contains None it will return None, as if the device was not
there.  This is not as serios as the error will most likely show itself
somewhere down the execution path.

I also added some documentation.

Joel