removed lots of useless env arguments

avoid multiple binding for the same term

bug fix: errors in complexe actions were not properly handled (the error was added to the state, but the function returned instead of called the success continuation)

nsl went from 12s to 11.1s

nsl example is done in 12s instead of 18 for me

started to do a huge rework of the way environement are handled, with the ultimate goal of using a functional implementation of environements

- corrected a bug in term.ml: pseudo normalization was badly done, variables must be collected in terms at each loop itaration to guarrantee that conditianal have a unique representation
- axiom_result type has been extended to include, in case of success, the information about was rule was used (symmetrical, encryption, decryption_

- added an example with the new syntax: helios.api