Keyringpath

changed the servalpath config param and related language to better reflect that it is a path to a serval keyring, rather than an instance directory.

to test, flash on two nodes, turn on MDP (with same keyring), and make sure they mesh.

includes https://github.com/opentechinstitute/commotion-router/pull/108 and https://github.com/opentechinstitute/luci-commotion/pull/161