Revert "Made the grid size customizable"

This reverts commit bed6daa0667a1ec87fc85246fc146898153a9102.
Adjust grid size automatically

Many users have asked for an option for customize the grid size. After
a initial approaching by adding a option to Preferences file, now
after Dan's suggestion it is made automatically.

NOTE: The grid size is now adjusted automatically
Fixed recovery of unsaved files

Fixed a issue related to the routine that recover an unsaved file
(autosaved) not be working as it should.

problem reported in this post: http://www.wings3d.com/forum/showthread.php?tid=377&pid=4709#pid4709
Fixed crash in saved views

Fixed a problem with saved views mangement that was crashing Wings3d
if the first item in the list was deleted and someone tries to save a
new view hitting the RMB over an empty place.

The problem was reported in this post: http://www.wings3d.com/forum/showthread.php?tid=736

NOTE: Fixed crash in saved views (Thanks to Stem)
Fixed normalization of vectore in move/scale/rotate

Fixed a bug with the routine to get vertex and point for
move/scale/rotate operations. When the vector was obtained from vertex
on two or three objects we could get undesired result during the these
operations.

NOTE: Fixed a bug with the routine to get vertex and point for
move/scale/rotate operations. (Thanks PuzzledPaul)
Fixed crash in Set Constrain->Percentage in Edge mode,

Was happening after have picked the axis for Set
Constrain->Percentage in Edge mode.

The problem was reported in this post: http://www.wings3d.com/forum/showthread.php?tid=718

NOTE: Fixed crash in Set Constrain->Percentage in Edge mode,
      Thanks Arg Arg.
Fixed flip command crash

NOTE: Fixed a crash caused by Flip command when the object has virtual mirror.
Thanks VladD for report it.