[QGIS-Developer] Processing 3.0 - porting guide

[Nyall Dawson]

Hi all,

Just a quick heads up - I've finally had the chance to finish off the
guide to porting Processing 2.x algorithms to 3.x API and merged it
into the API docs.

You can find it here:

https://raw.githubusercontent.com/qgis/QGIS/master/doc/porting_processing.dox


Hope it helps -- of course, more contributions and greater detail
would be very much appreciated. So if in your algorithm porting you
come across some traps/tricks you think should be added, please open a
pull request adding these!

Cheers,
Nyall