Initial splitting up the ChMatrix classes
Propagated changes from splitting ChMatrix.h into separate files throughout chrono
Fix unit PYTHON.
Rename ChTrasform.h to ChTransform.h
Rename ChTrasform class to ChTransform
Rename ChApiINPORT to ChApiIMPORT
rename all instances of lenght to length
rename all instances of Lenght to Length
renamed all instances of trasform and Trasform to transform and Transform respectively
renamed all instances of extimate and Extimate to estimate and Estimate respectively
fix small spelling mistakes
Remove unused demo code that wasn't being used/compiled
Reverting: old methods SetFrame_COG_to_REF etc were deleted because supposed to be unused, but they were used in the Chrono::SolidWorks add-in, that exported python code that called such methods.
SetNameString now takes its argument as a const value
Clean up ChShaftsBody::Initialize():

- this function is not virtual
- change type of return value to bool
- pass direction vector as const reference
Change return value type for ChShaftsCouple::Initialize() to bool.
Update cmake code to find Irrlicht so that it matches what unit_IRRLICHT uses to find Irrlicht
Fix issue with setting compiler flags for MSVC and change some variable names for clarity.
Small fix for atomic operations on armv5 platform
Benchmarks should not be run as tests, this might change in the future