glTF: constraine camera move in orbit mode

Not to get too close to / too far from the model.
Too close means move into the model.

Change-Id: Ie25d87c88093d4baaf98f13ab8239263b5e1bf66
(cherry picked from commit 9a670eb493f3760eb398c3f9d2296d979b608f95)

glTF: improve camera movement constraint

Stop moving only on the wrong direction.

Change-Id: Ic9e7f2e7814d9adcbcf707e7fb786bf17fac3125
(cherry picked from commit 09fe9db46615265c6c7119f2524d19335d0e0283)

glTF: camera movement constraint: use distance from the boundary box

... instead of distance from model center position.

Change-Id: I379ab5e32cc5009d0eb751c4808fecf0109d1e5a
(cherry picked from commit 2946c7c62718cb74feab554b5939ec340e6c4280)
Reviewed-on: https://gerrit.libreoffice.org/10084
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>