Improve handling of optional dependencies for Dorsal

Currently, really optional dependencies (SyFi and its dependencies, Trilinos etc.) sometimes cause compilation problems. Users need to be made aware of how to disable them, or they should be asked if they want them in the first place.

A common file/method naming structure should be enforced across different projects for CBC.Solve

Currently, twist and flow have a different file hierarchy and different names for methods in classes. This should be unified.