Heat provides tagging fuctionality for stacks, now tagging is
possible for stacks generated via murano also. To implement it,
added new config parameter `stack_tags` with default value 'murano'
and tagged heat stacks created during environment deployment with
`stack_tags` parameter's value.
Change-Id: Ib3f4027b78616c02cf3bbb210578df23d7e536d3
Implements: blueprint tag-murano-heat-stacks