Improvements to build scripts

Fixed 'bug' with org.eclipse.adt building where no jars would have been copied if ADT was installed in the user directory (even though eclipse correctly detects the plugin presence).

Added a new eclipse.dest property to clearly separate the responsabilities of eclipse.local. Now eclipse.local is only for reading plugins from user directory and eclipse.dest is only for specifying the destination of the eclim plugins. If no eclipse.dest is specified, defaults to eclipse.local.