Merge examples into release/2.4

[Frank Dellaert]

This page gives an amazingly simple way to merge in changes to one directory only:

• Check out directory only:

   cd gtsam-2.4
   git checkout origin/develop examples/

• Resolve compile errors
• Commit/push

[Frank Dellaert]

Much nicer than svn! A bit tedious to get it to compile but not hard.