Move visualization doc from overview to tutorials and remove overview dir
Move generation of advanced doc into own CMakeLists.txt

- Move find_package(Sphinx) into doc/CMakeLists.txt.
- Move Sphinx doctrees into build dir.
- Remove old Makefiles.
Rename ihs_lion_photo.JPG ihs_lion_photo.jpg
Only remove share/doc if WITH_DOCS is set.

- move WITH_DOCS to pcl_options.cmake.
Merge pull request #857 from jspricke/doc_fix

Cleanup docs