addedd batman parser, applyied DRY and created generic Parser

[gabri94]

I wrote a parser to work on a Batman-adv Topology, the json can be generated using "batadv-vis -f jsondoc".
To implement this parser i've also created new generic Parser class. This contains all the method that all the parser have in common.

I've also fixed a bug of the diff function.

[coveralls]

Coverage decreased (-1.64%) when pulling 07614d4 on gabri94:batman into e7b677f on ninuxorg:master.

[nemesifier]

give me 1 more day ;-)