common: Add cockpit_assert_bytes_eq() and cockpit_assert_data_eq()

These functions are used in tests to check if memory matches expected
and gives informative output if it doesn't match. This output could
be further enhanced to show a diff or some such, but for now it's just
a simple escaped listing.
agent: Add cockpit_channel_close_obj_option() function

This allows adding full JSON objects to channel close messages.
agent: Implement agent support for modules and resource1 payload

This adds support to cockpit-agent for listing and loading module
resources.

See doc/modules.md for information about how modules are laid
out on the system.

doc/protocol.md contains information about the resource1 payload
WIP cockpitwebservice resources as http
WIP junk