Modified the Standard and Orbit manipulators
to change the center of a rotation to the middle of the VIEW.

Also, I have changed the 'sensibility' of the mouse and, when doing
a drag, the scene is re-centered to allow the new rotation.

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Disabled the re-definition of 'boolean' in the JPEG plugin. It caused
a compile error with my compiler.
Merge branch 'master' of https://github.com/AdriCS/osg