Running ponzu-cms inside a docker container, and maintaining
data files in a volume (or several) was not possible with the
previous directory schema without copying files or binaries
to the volume.

This commit adds several environment variables to allow the
administrator to specify paths for directories while
retaining backwards compatibility.

- PONZU_DATA_DIR : is the directory where all the data and other
                   directories will be stored, still the other
                   directories can be controlled by the other env
                   variables.

- PONZU_TLS_DIR : is the directory to store devcerts and autocerts

- PONZU_ADMINSTATIC_DIR : directory where the admin static files are
                          served from.

- PONZU_UPLOAD_DIR: upload files directory

- PONZU_SEARCH_DIR: index directory for searches

* [deps] acme/autocert: update to latest with support for "http-01" challenge

* [core] system/tls: implement handler for "http-01" challenge

This PR enables admins to disable/enable CORS and GZIP from within the admin CMS configuration page. Both are enabled by default.

Note: currently, the GZIP implementation is 100% on the fly, for every qualifying API endpoint request. This could add significant CPU usage, but dramatically decreases bandwidth. Will be considering other better implementations, but for now YMMV.

Possible optimizations:
- pooling gzip Writers vs. creating a new one for each response
- caching gzipped responses (in memory? on disk?) 
- enforcing size threshold (only gzip content larger than N bytes)