Merge branch 'cmake' of https://github.com/USGS-Astrogeology/isis3_cmake into cmake

  # Set up output directory and a temporary directory for building

  set(docBuildFolder   ${CMAKE_BINARY_DIR}/docBuild)

  set(appDataFolder    ${docBuildFolder}/Application/data)

  set(docInstallFolder ${CMAKE_INSTALL_PREFIX}/doc) # Final output documentation

  set(docInstallFolder ${CMAKE_BINARY_DIR}/docs) # Final output documentation

  # Clean up existing files

  execute_process(COMMAND rm -rf ${docBuildFolder})

  message("Building object documentation")

  build_object_docs()

  # copy the built docs in the build directory over to the install directory on install

  execute_process(COMMAND cp -rf ${docInstallFolder} ${CMAKE_INSTALL_PREFIX})

  message("Finished building object documentation!")

endfunction(build_docs)