[QGIS-Developer] [WIP] GRASS Processing port to new API

[Médéric Ribreux]

Hello devs,

just a simple mail to tell you that I am currently working on QGIS3 
Processing port of GRASS plugin.
You can read the code in my forked QGIS git repository:
https://github.com/medspx/QGIS/tree/ProcessingPortGrass72

For the moment, about 50% of the job is done:
- I have used the new QgsProcessing framework for parameters (I have 
used modifications of processing/parameters.py made by Nyall in the SAGA 
port).
- I have modified description files according to this new framework.
- I can launch most of the algorithms for rasters and vectors (and some 
imagery).
- I have also worked on improving layers management (importing/exporting 
into/from temporary GRASS DB).

I still need to work on the following points:
- Adapt and factorize ext/ scripts to the new framework.
- Multiformat support for vector and rasters.
- A better support for OutputFiles (HTML and text files).
- Add new GRASS7.2 algorithms (less than a dozen).
- Verify all description files to support the new parameters introduced 
into GRASS7.2.
- Port and improve unit tests.
- Try to fix all bugs linked to unicode support under MS-Windows.

I am going offline for the next 3 weeks and I think I'll be able to make 
a (decent) PR at the end of this period of time.

I really hope that QGIS3 will have GRASS Processing in its first 
release...

Cheers!
-- 
Médéric RIBREUX
https://medspx.fr