Command-line parameter overwriting

[dfbarrero]

Change any parameter in the configuration files by command-line with an interface similar to:

r2p2 --scenario conf/scenario.test.json --x 10 --y 400

[pedrosanchezr]

I have merged in develop a simple implementation for this, but it could cause errors if the user enter a wrong set of parameters or spaces between the values without quoting them.

For example:

--start [10, 20] would cause errors as "argparse" will treat it as 3 extra parameter "--start", "[10" and "20]"

In that case the user should use quotes:
--start "[10, 20]"

[pedrosanchezr]

PR: #32

[dfbarrero]

Please, make parameter overriding recursive. We need to overwrite not only parameters in the scenario, but in any config file. A clear example of this is to change the robot initial position from the command line:

r2p2 --scenario foo.json --x 150 --y 200

[dfbarrero]

Perhaps, we should add a new feature to show the final configuration that the simulator is using, something like:

r2p2 --scenario foo.json --x 150 --y 200 --show-config

This should ease configuration debugging.