Medium: parse: Resource sets in location constraints (fate#315158)

Adds support in cibconfig for resource sets and templates
in location constraints. Also adds support for regexes in
location constraints.

Syntax:

location <id> /<regex>/ ...
location <id> { <resource-set> } ...
Low: parse: Stricter parsing of resource names

Require that resource names start with an alphabetic
character or _, # or $. Refuse empty resource-matching
patterns.