Add noise to continuous data in mixed KSG calculator

[jlizier]

This is the only KSG calculator which neither has property for adding a small amount of noise to the data, nor does this by default. Both should change, in particular because the conditional where we have multiple occurrences of a value in one dimension alters the neighbour counts away from what they are assumed to be (see closed issue #8)

[pmediano]

Note: this applies only to the conditional MI mixed KSG calculator (which in fact needs a full revamp). Noise in continuous data is implemented and set to 1e-8 by default in lines 210, 286, and 422 of MutualInfoCalculatorMultiVariateWithDiscreteKraskov.java.

[jlizier]

thanks, yes I should have been more clear on that!