Support for adding new tags to instances based on existing ones

[m0un10]

This PR adds functionality to graffiti monkey to allow for new tags to be added to instances based on existing ones. For example, if our instances were named dev-01 and dev-02, we could add a rule to add an owner=devmgr@mycompany.com and team=dev tag for any name starting with dev. This is achieved by regular expression rules. For example:

_instance_tags_to_add:
 - key: Name
   matches:
     - match: ^dev.*
       description: Development
       tags_to_set_if_match:
         owner: devmgr@mycompany.com
         team: dev

Existing functionality is not impacted by this addition. The instance tagging is not triggered unless _instance_tags_to_add: is included in the configuration. This tagging can be disabled with --noinstances (as per the same convention used for volumes and snapshots) and it supports dry run with --dryrun