[FEATURE] Add universal S3 provider support

[nischay876]

Description

Allow configuring any S3 host, such as AWS, Storj.io, Digital Ocean, and more.

nischay876@6c03fce

Also try to support both "public" and "private" modes for providers.

[tycrek]

Will plan for 0.15.0. (See here for more info: #172 (comment))