Show pyapi version

[olofhagsand]

Show pyapi version.
Both by (1) directly invoking the program; and (2) a method with which the clixon controller can fetch the version.
Proposal: -V command-line option show version and quits (same as clixon).

Reference: This is how versions are shown in the controller, but lacks pyapi version:

# op show version
Controller: 	0.3.0.PRE
Clixon: 	6.6.0.PRE
CLIgen: 	6.6.0.PRE

See also: clicon/clixon-controller#101

[YotaYota]

I can fix this. I suggest that we merge #6 first since it changes the usage from getops to argsparse in order to parse CLI arguments.

I got something in the pipe for this

[krihal]

$ clixon_server.py -V
1.0.0-PRE

[krihal]

Added.