Improved command line parsing

[waveform80]

There's too many options in config which should be specified (or potentially specified) directly in commands (capture count, delay, recording format, etc). Additionally, the tab-completion leaves something to be desired, and the grammar is weird in places ("set" for configuration options on the client, but a whole bunch of stuff other than "set" for configuration options on the server). Ideally we ought to switch to a simple parser (pyparsing? hand-crank a rdp?) and use its output to improve completion.