Added all constructs applicable to untraceable SUT

* Add aPC, ITC, ETC, PSC, BTC, AAC, CTC and LSC
* Dedicated normalization function handles normalizing in (almost) all constructs, handles empty rows/columns, and creates filters (nn_in, nn_out)
* All constructs give the same consistent output: A, S, nn_in, nn_out, Z, F_con
* Automatic generation of primary production matrix (E_bar)
* Automatic generation of subsptitution matrix and alternate activity matrix in multi-regional context
* A certain number of "helping functions" outside of the class definition
* I tried to be thorough on the documentation
* Unit tests for all, in a separate class