0027301: CMake: export targets for OCCT

0027301: CMake: export targets for OCCT

Enabled creation of CMake target files (one per module) for OCCT at install time.
Variables enumerating available OCCT toolkits by module are added in CMake configuration file.
Added check of availability of OCCT modules specified by OpenCASCADE_FIND_COMPONENTS variable.
Location of CMake configuration and target files in Windows layout is changed to $INSTALL_DIR/cmake (thus common for all configurations), to be found by standard search logic of CMake find_package() function.