Feature/namespace refactoring

Massive refactoring intended to clean up the nsxlib interface prior setting up python bindings:

• SX namespace renamed to nsx
• removal of inner namespaces (e.g. Data, Geometry ...)
• reorganization of the include sections according to coding policy (see wiki)
  • include reorganized according to their corresponding library
  • within each block, the includes are sorted
  • removal of many unused includes
  • removal of several redundant includes