serial interface: add command parser for protocol

[dhebbeker]

Create a command parser which is capable to interpret the commands from serial interface according to the defined protocol.

See WIP.

Acceptance criteria:

• It is OK for this version to respond with dummy responses (format does not need to follow protocol)
• All arguments of the commands shall be understood (test by echo the values to serial interface)
• Dummy functions for the commands shall be called (test by echo a string on serial interface)

Depends on:

• 58

• 59 or #77