Tune-able timeouts in http.Server

[broamski]

Is your feature request related to a problem? Please describe.
When uploading large files to vault for processing by a plugin, last-mile or slower connection users experience i/o timeout errors as the http.Server ReadTimeout of 30 seconds is met.

Describe the solution you'd like
Allow http.Server timeouts to be user configurable.

Describe alternatives you've considered & Explain any additional use-cases
The obvious answer is "alter the process to use a smaller value that also represents the submitted payload" (hashes, etc.). This is an ideal future state, but several legacy systems would require a non-trivial amount of work to support this change.