Fix CMake install; file permissions

Install some python scripts explicitly as executable
and use not the USE_SOURCE_PERMISSIONS option for directories
(which then depends on the file perm. during clone)
diff --git a/libtrellis/CMakeLists.txt b/libtrellis/CMakeLists.txt
index d838d44..21b2ace 100644
--- a/libtrellis/CMakeLists.txt
+++ b/libtrellis/CMakeLists.txt
@@ -168,4 +168,6 @@
 install(DIRECTORY ../database DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROGRAM_PREFIX}trellis PATTERN ".git" EXCLUDE)
 install(DIRECTORY ../misc DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROGRAM_PREFIX}trellis)
 install(DIRECTORY ../util/common DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROGRAM_PREFIX}trellis/util)
-install(DIRECTORY ../timing/util DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROGRAM_PREFIX}trellis/timing USE_SOURCE_PERMISSIONS)
+install(DIRECTORY ../timing/util DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROGRAM_PREFIX}trellis/timing)
+install(PROGRAMS ../timing/util/cell_html.py DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROGRAM_PREFIX}trellis/timing/util)
+install(PROGRAMS ../timing/util/cell_timings.py DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROGRAM_PREFIX}trellis/timing/util)