Easier to read aliases in docstrings

[leouieda]

Right now, the parameter aliases (region for R, projection for J) are listed above the parameter descriptions. This is a bit hard to read because you have to go back and forth between the alias list and descriptions.

It would be better for the parameter names to be listed as the long alias and include the original 1 letter name next to it.

For example, this is how it is now:

Aliases
-------
* J = projection

Parameters
----------
J : string
    The projection bla bla bla

and what I would like to see is:

Aliases
-------
* J = projection

Parameters
----------
projection (J) : string
    The projection bla bla bla

This can be in the fmt_docstring decorator in gmt/decorators.py. It might make it easier to define all descriptions of the GMT module arguments outside of the docstring (like we do already for the common ones, like J and R). The Python specific arguments, usually for passing in data, don't have aliases and could be specified normally on the docstring.

[weiji14]

Resolved by #383 (napolean style docs) and #473 (document only the long alias). No more mentioning of short aliases, and we define the type in the brackets. I.e. projection (str) instead of projection (J).