* avoid necessity of special chars in autoconfig specific environment variable names

* assure env file is generated for mail container
* let generated searches.ini file contain an empty index shards section by default

* ignore data folder completely
* use updated version of vufind-httpd image
* let env container write with uid:gid of project root
* let composer event handlers being called with correct uid:gid
* add xsl and dom php extensions

* avoid high cpu usage by endless loops