general context provider

[jmatejcz]

Is your feature request related to a problem? Please describe.
For now Context provider was implemented for megamin but it could be usefull as general feature for more agents #687

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[maciejmajek]

Looks a bit like the get_state mechanism from StateBasedAgent

[jmatejcz]

Looks a bit like the get_state mechanism from StateBasedAgent

you are right, they work similar, but StateBasedConfig seems to be only for ros topics. General solution could probably be build based on both