Added cross package css/less import support

Actually, I meant something like this
```
			IResource importRes = res.resolve(importNameMatch);
			URI uri = null;
			if (importRes.exists()) {
				uri = importRes.getURI();
			} else if (importNameMatch.contains("/") && !importNameMatch.startsWith(".")) { //$NON-NLS-1$ //$NON-NLS-2$
				// Resource not found using relative path to res.  If path is not relative (starts with .)
				// then try to find the resource using config paths and packages.
				uri = aggregator.getConfig().locateModuleResource(importNameMatch);
			}
			if (uri == null) {
				throw new NotFoundException(importNameMatch);
			}
			
			String importCss = null;
			importCss = readToString(
					new CommentStrippingReader(
							new InputStreamReader(
									uri.toURL().openStream(),
									"UTF-8" //$NON-NLS-1$
									)
							)
					);
```