mrtg-ubnt-probe.py: Drop DictDotLookup, implement the reverse, i.e. convert (user-specified) dotted notation to the equivalent dict/list syntax.
mrtg-ubnt-probe.py: Use set() rather than dict().keys() for more efficient (?) duplicate filtering.
mrtg-ubnt-probe.py: Pass HTTP response directly to JSON parser, supposedly this is more efficient.