sci-geosciences/grass: bump to -7.0.1

sci-geosciences/grass: bump to -7.0.1

Inherit python-single-r1 eclass, three USE flags added and two removed
to update new configure options; set slot operators on required deps,
patches to fix build issues; install desktop file via make_desktop_entry,
tidy EAPI style vars
set new proxy-maintainer 'wraeth', add proxy-maintainers herd in metadata
along with new use flags

Gentoo bug: #514514

Package-Manager: portage-2.2.20.1