Making map manager srvs work when loading map from tmap files.

[adambinch]

Services modified to work when loading topological maps from tmap files:

• /topological_map_manager/get_tags
• /topological_map_manager/get_node_tags
• /topological_map_manager/add_tag_to_node
• /topological_map_manager/get_tagged_nodes

[gpdas]

6b12111 fixes #23

(Leaving this here to autoclose the issue when this is merged.)

[Jailander]

I tested this will merge