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_purge.c

@@ -160,7 +160,7 @@ xbps_purge_pkg(const char *pkgname, bool check_state)
 	/*
 	 * Execute the purge action in REMOVE script (if found).
 	 */
-	if (chdir(xhp->rootdir) == -1) {
+	if (chdir(prop_string_cstring_nocopy(xhp->rootdir)) == -1) {
 		rv = errno;
 		prop_object_release(dict);
 		xbps_error_printf("[purge] %s: cannot change to rootdir: %s.\n",
@@ -194,7 +194,8 @@ xbps_purge_pkg(const char *pkgname, bool check_state)
 	/*
 	 * Remove metadata dir and unregister package.
 	 */
-	if ((rv = remove_pkg_metadata(pkgname, xhp->rootdir)) != 0) {
+	if ((rv = remove_pkg_metadata(pkgname,
+	    prop_string_cstring_nocopy(xhp->rootdir))) != 0) {
 		xbps_error_printf("%s: couldn't remove metadata files: %s\n",
 		    pkgname, strerror(rv));
 		return rv;