backport release build script
README: add instructions on how to convert HMTL to RST

useful when missing files are detected
re-add guardtime signature provider doc

this was missing in the initial import
gcry provider doc: fix some of its nits
gt sig provider: amend info on how to supply user credentials
Merge branch 'v7-stable' into v8-stable

Conflicts:
	source/configuration/cryprov_gcry.rst
Merge branch 'v8-stable'