Moving to use Commons package in variable ts
Ids are now generated from 1
Not ISO8601 date handled

Throws illegalArgumentException
Refactored: use generics, sanity checks

* Use generic List classes instead of specific ArrayList classes on the
  left hand side

* Adding sanity checks
New VariableTimeseriesEngine introduced

* Old one had references to the whole
  namespace-structure-structure_instance thing, removing all that here
  and bringing in the binding with the IDEngine

* Keeping the old one still under "old" for referencial purposes, it
  will be deleted in just a few more commits

* Testbed updated with references
    VariableTimeseriesEngine -> VariableTimeseriesEngineOld

* Adding tests
Fixing error in naming

* It was named cache engine test but was actually testing the
  variableTimeseriesEngine (old)