ENH: Framework for java dependency scanner.  Right now it does nothing but always reports success.  This is enough to get the Java test to pass with the new generator because the old implementation did not do dependencies anyway.

BUG: Replaced previous fix with an implementation of properly formatting the custom build code in the generated file.

ENH: Replaced OutputEcho/pre-echo/post-echo with AppendEcho.  This allows for more flexible echo specifications and better preserves echo text.

ENH: Added ConvertToQuotedOutputPath method and used it to properly generate external object references with spaces in the path.

ENH: Converted some ConvertToRelativeOutputPath calls to ConvertToOptionallyRelativeOutputPath in preparation for making ConvertToRelativeOutputPath always convert.  Some of these might be able to be switched back but we will first have to test what paths can be relative in the generate VS project files.

ENH: Converted some ConvertToRelativeOutputPath calls to ConvertToOptionallyRelativeOutputPath in preparation for making ConvertToRelativeOutputPath not check CMAKE_USE_RELATIVE_PATHS.

BUG: The path to the source file in a compile line should be made relative only when CMAKE_USE_RELATIVE_PATHS is on.

ENH: Merged implementations of ConvertToRelative*Path methods.  The main ConvertToRelativePath method is now in cmGlobalGenerator.  It converts paths only if they are at least inside the deepest common directory between the top-level source and build trees.  Each cmLocalGenerator instance calls this global method with its own output directory as the "local" argument from which paths are relative.  Added separate ConvertToOptionallyRelative path that pays attention to the CMAKE_USE_RELATIVE_PATHS option.