Use plugins per protocol approach

[mullermp]

Went back and forth on this a lot over the past few months. This approach is to just use one protocol per plugin.

Main advantages:

• protocols can set their own configs onto the client, like for codecs, simple json, or even stubbing.
• no special casing of welds - protocols are just plugins. Ordering still is necessary at the weld level.
• Protocol handlers act on listeners (over the wire) instead of on parsing a body into a string io and then parsing into a data structure.

Quirks (maybe or maybe cons):

• no protocol config option - protocols can be removed or swapped out at the client class level like any other plugin
• new protocols are also plugin/handler based