Split TLEM 1 and 2 models

[melund]

This PR aims to separate the TLEM 1 and 2 models.

A new folder AAUHuman/LegTLEM2 will hold all TLEM 2 code where intermingled TLEM1 code will be removed.

The old LegTLEM folder will continue to hold old code with intermingled TLEM1/2 code. Using the TLEM1 model from this folder will trigger a deprecation warning.

In order to ensure the correct Git history the LegTLEM folder has been copied to LegTLEM_Old, so LegTLEM2 can eventually have the unbroken history.

[melund]

@depierie. Just a heads up.

We decided to split the TLEM 1/2 model implementation. So code is not intermingled with BM_* statements. It should make code much simpler. This PR does exactly this.

We also plan to issue a deprecation warning when users run with TLEM 1.

[melund]

I have added the suggestion from @toerholm's review. All use of the BM_LEG_MORPHOLOGY switch have been removed from the code base, and all TLEM2 code have been removed from the LegTLEM1 folder. So now it is a clean split between TLEM 1/2.

This will be merged once tests pass.