(PUP-3272) Remove YAML on the network

This removes b64_zlib_yaml, but keeps yaml as a format.
An attempt is made to change yaml to pson for networking - do not know
if that has been achieved.

3 tests are failing.
(PUP-3272) Remove vendored load of safe_yaml
(PUP-3272) Change deprecation warning for YAML on nw to errors

This changes the deprecation warnings about YAML use on the network
to errors. As a consequence tests are updated to reflect the change.
(PUP-3272) Fix broken test

The test was broken as it changed how a body war rendered; rather
than using the body, it always rendered either data or the body as pson
- the intention was to use the raw body.
(PUP-3772) Remove commented out base64 encoded yaml network format

The base64 encoded yaml network format should have been removed.
It was only commented out.
(PUP-3272) Remove safe-yaml parameters fom YAML load

These parameters have no effect when regular YAML is used.
(PUP-3272) Change Status yaml deserialization to support psych

This changes deserialization of a Status instance to use
a custom initialization (based on params hash). The implementation
is in a PsychSupport module to make it more visible and easier to add to
other classes needed the same support.

Since this change is not compatible with 1.8.7, the report_spec test
that depends on this functionality is restricted to not run on Ruby
1.8.7.
(PUP-3272) Remove special treatment of YAML encoded parameters

When it was allowed to pass YAML on the network it was also allowed to
pass parameters that were YAML encoded. The 3x logic had deprecation
warnings in place for these places.

Now in 4x, when YAML is no longer supported, the request parameters are
simply always strings. If someone yaml encodes data and sets it in a
parameter this has no special meaning - it is just a string that happens
to contain yaml (e.g. "--- \n 'foo'\n"). 

This means that it is now ok to have parameters that look like YAML but
it is not - this could cause problems earlier.
(PUP-3272) Simplify logic where yaml param was special case

Also remove dead comment.
(maint) Change phrasing of error message about Yaml not supported

This changes message from "are not supported" to "is not supported"