cmake: do not hardcode absolute paths in the installed CMake module files

Hardcoding abslotue install paths in the CMake module files totally
breaks the cross-compilation: it makes impossible to be used in a
sysroot because the hardcoded paths are the ones of the target, whereas
they should point to the sysroot location.

This patch adds non-templated CMake module files for octomap,
dynamicEDT3D and octovis, uses the CMake find_library and find_path to
set the variables *_LIBRARIES and *_INCLUDE.
It also get rid of the unused *_LIBRARY_DIR variable in these CMake
module files.

Only the installed CMake module files are changed. The templated ones
are still needed for combined package build.