Isolate flavour differences

[eperott]

In order to support different versions of Cassandra we're using the concept of flavors in ecAudit, which basically mean we maintain different branches of ecAudit - one for each supported version of Cassandra.

The differences between flavors is mostly limited to some specific parts of the code, but it is scattered around the code base which makes it error prone and time consuming as we're merging features/fixes between flavors/branches.

We should try to make this more explicit in our design by breaking out favor-differences into distinct classes or methods with intention-reviling names.