BUG: make sure the pyramid region size is never reduced to 0

As pointed out by Remi Blanc on the mailing list.

git-svn-id: https://svn.bigr.nl/elastix/trunkpublic@4167 4d348492-3962-11de-aa85-65a2020054a3
DOC: updated the manual a bit 

according to a comment of Ronald van 't Klooster

git-svn-id: https://svn.bigr.nl/elastix/trunkpublic@4191 4d348492-3962-11de-aa85-65a2020054a3
SK:

-ADD: copy elastixlib.cxx to trunkpublic


git-svn-id: https://svn.bigr.nl/elastix/trunkpublic@4196 4d348492-3962-11de-aa85-65a2020054a3
SK:

-ADD: copy elastixlib.h to trunkpublic



git-svn-id: https://svn.bigr.nl/elastix/trunkpublic@4197 4d348492-3962-11de-aa85-65a2020054a3