__getattr__ shortcut for calling GRASS display modules

[chaedri]

• Shortcut allowing users to call GRASS display modules ('d.*) with class method .d_*.
• Example of usage in jupyter_integration.ipynb
• Typo fix and black formatting

These modifications are part of an on-going Google Summer of Code project, Improved Integration of GRASS GIS and Jupyter Notebooks. You can find more information here. You can test out the functionality in Binder here:

https://mybinder.org/v2/gh/chaedri/grass/non-interactive-display-update?urlpath=lab%2Ftree%2Fdoc%2Fnotebooks%2Fjupyter_integration.ipynb

[chaedri]

There are a couple things that need improvement still:

1. Error Handling. If the user passes an incorrect or incorrectly formatted command, say .d_raster instead of .d_rast, it returns two errors, one that results from the try: statement and one that results from the except: statement. I think this is unexpected behavior...
2. There might be other errors that need handling. For example, if you pass incorrect keyword arguments such as d.rast("elevation") instead of `d.rast(map="elevation"), the error isn't very useful.
3. I haven't tested all the `d.* modules.

[wenzeslaus]

Sweet and simple, just the error handling needs some more work.

Please, include an example in the notebook, so that others can try easily.

[wenzeslaus]

@chaedri It seems to me that the message "Module must begin with 'd_'" needs little more clarification, but let's leave that for some documentation PR. (I'm thinking module vs GRASS module, "must begin with" vs display commands, and including the name of the command.