Switch to python and Jinja2 for the dovecot container

dovecot/Dockerfile

@@ -3,12 +3,10 @@ FROM alpine:edge
 RUN echo "@testing http://nl.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories \
  && apk add --no-cache \
      dovecot dovecot-sqlite dovecot-pigeonhole-plugin dovecot-pigeonhole-plugin-extdata \
-     rspamd-client@testing \
-     bash
+     rspamd-client@testing python py-jinja2
 
-COPY conf /etc/dovecot
+COPY conf /conf
 COPY sieve /var/lib/dovecot
+COPY start.py /start.py
 
-COPY start.sh /start.sh
-
-CMD ["/start.sh"]
+CMD /start.py