Simplify the make process

[rowleya]

The make process has been improved with installation, but could be simpler for those who have all the code in front of them. Current issues:

• The clean is not quite working correctly and tries to delete the wrong modified source folder
• Sometimes install make symlinks, but it should actually copy files into place
• When the code is all checked out in a single structure, there is no need to "install" as such - the build folder could be referenced instead

[Christian-B]

Ideally the locations used by build will mirror those used by install (except for the parent directory)

That way if build is done in place no install is needed at all.

And higher level build processes can be identical except for environment variable that point to where all files are located.