New configuration scheme changes, round 1.

- Configuration file 'xbps-conf.plist' has been splitted off into
  two files: conf.plist and repositories.plist. By default they
  are stored in etc/xbps.
- Changed some members in xbps_handle struct, mostly to make it easy
  to change its value in {cache,root}dir and conffile.
- Made xbps_init() release proplib objects as soon as we don't need
  them, that way it uses 35% less of memory or in some cases even more.

There will be another commit that will implement to read new virtualpkg
settings by the user, as specified in:

	http://code.google.com/p/xbps/issues/detail?id=12

lib/package_unpack.c

@@ -172,7 +172,7 @@ unpack_archive(prop_dictionary_t pkg_repod,
 
 	preserve = update = false;
 
-	if (chdir(xhp->rootdir) == -1) {
+	if (chdir(prop_string_cstring_nocopy(xhp->rootdir)) == -1) {
 		xbps_error_printf("cannot chdir to rootdir for "
 		    "`%s-%s': %s\n", pkgname, version, strerror(errno));
 		return errno;