[gf/wrap] Add setter for tail and improve wrapper

- wrapper : add possibility of calling_pattern to the setter functions
  of a property
- gf : make the tail writable, by adding a setter to the property
[operators] Wrap the dagger function for many_body_operators

- dagger (op) returns the dagger operators.
Add an include for type_traits

This is needed because newer versions of boost don't include
it anymore.
[plot] pass kwargs to plot, remove check
[mc] broadcast the average sign
Merge branch '1.2-dev' of github.com:TRIQS/triqs into 1.2-dev
 Split implementations of project() for hilbert_space/sub_hilbert_space

 * Removed a check in the hilbert_space version