Updated the licence info and header for each file.Moved backends in separate folders
Prepared first stage of code reorg:1. moved type def in lustrespec.ml2. moved constructor and basic functions in corelang3. Modified eexpr with prenext quantifiers
Added declaration/definition of stateless/stateful nodes. The 'function' keyword is for stateless nodes only, the 'node' keyword is any kind of node. Improves compilation and paves the way for more optimizations.