Reorganization of classes, Add class Fig LinearFig

[jjdishere]

There is a problem of DirFig.toDir, it may be not def equal to Ray.toDir otherclass.toDir. Do we need to force they are the same? Is everything ok if we keep this def equal?
Or do we need to bring DirFig into Class.lean then define toDir as early as that? (so there will be no other defs of toDir)

[jjdishere]

It is possible to reorganize whole class structure.

1. Fig means have carrier,
2. Linear means any 3 pts in Carrier is colinear,
3. DirFig means Fig + has toDir
4. ProjFig is LinearObj (which cannot extends DirFig, instead Coe DirFig ProjFig, Line is only ProjFig) Maybe ProjFig is exactly Linear?
5. Intersect should be defined for any 2 Carrier. In Circle files, show it is equiv to r >= d.