Set strategies in Trotter evolution
Added functions to compute the MPS size.
Added explicit names to the different truncation methods.
Replace true -> normalize to make the Trotter strategy more explicit.
Reorganize Trotter algorithms, so that the strategy is more clear and code is factored into the Unitary objects
limited_svd() now has less optional arguments
Remove useless qualifiers.
Extract flags out of truncate.cc so that they are created _after_ the flags object
Make it explicit in set_canonical() that we at least truncate zeros or use the default tolerance.
Improved debugging information from simplify() and the Trotter routines.
Merge branch 'master' of https://github.com/juanjosegarciaripoll/mps