handle ipp/ipps explicitly

[jswolf19]

closes #19

The http request scheme is currently hard coded, so using https or ipps is not currently supported.
ipp requests do not currently default to port 631.

If ipp or ipps is the scheme and a port is not provided, the port should default to 663 (and not 80/443).

• ipp: https://www.rfc-editor.org/rfc/rfc3510#section-4.2
• ipps: https://www.rfc-editor.org/rfc/rfc7472.html#section-3

This would be a breaking change for usages where

• the uri scheme is ipp, but a port is not provided and a connection on port 80 is desired
• ipps/https are specified but an insecure connection on port 80(when port is unspecified) is desired

This should solve any issues addresed by #16 but won't break usages that currently supply an ipp uri scheme.

[danielklecha]

It appears that this repository is currently no longer actively maintained. However, the requested fix (along with several other improvements) is now available in an actively maintained fork: SharpIppNext.