cmake: Add --open option for IDE generators

Auxiliary/bash-completion/cmake

Help/manual/cmake.1.rst

Help/release/dev/cmake-open.rst

Modules/CMakeFindSublimeText2.cmake

Source/cmExternalMakefileProjectGenerator.cxx

Source/cmExternalMakefileProjectGenerator.h

Source/cmExtraSublimeTextGenerator.cxx

Source/cmExtraSublimeTextGenerator.h

Source/cmGlobalGenerator.cxx

Source/cmGlobalGenerator.h

Source/cmGlobalVisualStudioGenerator.cxx

Source/cmGlobalVisualStudioGenerator.h

Source/cmGlobalXCodeGenerator.cxx

Source/cmGlobalXCodeGenerator.h

Source/cmake.cxx

Source/cmake.h

Source/cmakemain.cxx