Move McLachlan-specific code out of Kranc

[barrywardell]

There is come code in CalculationFunction which should be moved out of Kranc and into McLachlan or other evolution thorns which require it. There are two specific cases I am aware of:

• In assignLocalFunctions there is code which conditionally sets local copies of any variable matching the pattern "eT" based on the stress_energy_state parameter. Kranc unconditionally copies any local variables which are used in the LHS back to their grid functions.
• In CheckGroupStorage, the TmunuBase groups are explicitly ignored.

Not only do these not belong in Kranc, but they can also lead to confusing bugs. For example, in McLachlan it is possible to use the stress tensor in the RHS of a calculation unconditionally, but it can only be used in the LHS if the stress_energy_storage parameter is set. Trying to use it in the LHS without setting the parameter doesn't give any warning or error until the sefault when running the simulation.

[barrywardell]

This is related to/a duplicate of issue #3.