Refactor internal resource location APIs and initialization
Rename cmSystemTools::FindExecutableDirectory to FindCMakeResources. Teach it to compute the locations of cmake, ctest, cpack, ccmake, and cmake-gui executables, and the location of CMAKE_ROOT. Provide this information from static cmSystemTools::Get<resource>() methods. Refactor code that needs these locations to use the new APIs. Teach FindCMakeResources to use the OS X system API to lookup the executable location. When running from the CMake build tree itself, leave a file in the tree that FindCMakeResources can use to read the location of the source tree. This avoids the need to compile the source tree location into a binary that may be installed and used without the source tree. Teach the QtDialog on OS X to create a "cmake-gui" symlink in the build tree next to "cmake" and the other tools, as is already done in the install tree for the application bundle. This ensures a consistent set of executables are available in one directory.