Attempt to solve Issue #26 (Motes change names while programming)

This PR solves #26 in different ways
 1. introducing a udev-rule which generates systemlinks for nodes at /dev/inga/node-* and uses them instead of ttyUSB* (no more automatic renaming)
 2. introducing a way to get static handles for the ttyUSB* by using /dev/serial/by-id/* for setups without this udev-rule
 3. fallback mode to ttyUSB* if all of them fail