Refactor directions_map loading

Instead of defensively loading the map then relying on an instance
variable, we'd better have a helper method we can call from anywhere.
This has several benefits:
- it's much less fragile, it won't break with a nil variable in the
  future
- it avoids having conditions to load the map, which could diverge from
  the real needs in the future
- it's better from an OO perspective, it's encapsulated and
  self-sufficient so it can be tested more effectively, or even mocked
  in views/methods that use it
- it's easier to read and understand
Refactor member_map loading

Same reasons as previous commit, see 3d39728
Refactor organizations_map loading

Same reasons as previous commit, see 3d39728
Avoid false positives when matching projects in projects/index page