Re: [release planning] GRASS GIS 8: create new release branch

Hi devs,

After a lot of editing and discussions in the following PR I meanwhile
also believe that it is becoming the preparation of the master branch
for G8:

"GRASS GIS 8.0 changes"
https://github.com/OSGeo/grass/pull/1597

That means:
- merge this PR into the master branch (it is not perfect, but let's
move on and create separate PR(s) for the Windows related issues)
- branch off a "8.0.0alpha" branch, just as a "throw away/ignore later" branch
- create at a later stage the official "release_branch_8_0" after
having gained some experience with the "throw away" 8.0.0alpha branch.

If there are no objections I'd merge PR 1597 in the next days.
Note: the changes include (except for Windows) the simplification of
the startup script name (grass79/grass80 --> grass).

Markus