sculpt: read config from /rw/config/<VERSION>/

By incorporating the sculpt version into the path where customizations
are stored, we can update and roll back sculpt versions without risking
configuration incompatibilities. By default, the sculpt version
corresponds to <genode-dir>/VERSION.

repos/gems/run/sculpt/leitzentrale.config

@@ -157,6 +157,7 @@
 								<dir name="tmp"> <ram /> </dir>
 								<dir name="share"> <dir name="vim"> <rom name="vimrc"/> </dir> </dir>
 								<rom name="README"/>
+								<rom name="VERSION"/>
 							</fstab>
 							<start name="/bin/bash">
 								<env name="TERM" value="screen" />