Success case:
- the path endpoint creates and sends a LR_StatusMessage upon
successful path creation
Failure case:
- an intermediate hop creates and sends a LR_StatusMessage upon
failure to forward the path to the next hop for any reason
Both cases:
- transit hops receive LR_StatusMessages and add a frame
to them reflecting their "status" with respect to that path
- the path creator receives LR_StatusMessages and decrypts/parses
the LR_StatusRecord frames from the path hops. If all is good,
the Path does as it would when receiving a PathConfirmMessage.
If not, the Path marks the new path as failed.
LR_StatusMessage is now used/sent in place of PathConfirmMessage
This commit refactors functionality from the Router class into separate,
dedicated classes.
There are a few behavior changes that came as a result of discussion on
what the correct behavior should be.
In addition, many things Router was previously doing can now be provided
callback functions to alert the calling point when the asynchronous
action completes, successfully or otherwise.
