[feature] allow regex and fetcher for custom project/collector

[digizeph]

We should allow users to provide custom regex and fetch method (e.g. local file, http, ftp, or object storage) to allow users index custom collectors/projects. This would enable broker to be used at non-public BGP data archives.

The regex and fetch should be configured via environment variables and commandline flags (e.g. --project --regex to indicate custom regex and projects).