This cleans up most of the warnings from sphinx (broken :doc: links,
broxygen role misuses, etc.). The remaining ones should be harmless,
but not quick to silence.
I found that the README for each component was a copy from the actual
repo, so I turned those in to symlinks so they don't get out of date.
I made a light pass over the text. Switched the includes over to the
new btest-include and adapted the other TEXT-EXECs a bit.
Also includes more tweaking all over the Sphinx setup.
Include explanation of various Notice::policy hook actions.
Add two btest scripts. framework_notice_hook_01.bro shows adding an
action to the n$action set while framework_notice_suppression.bro shows
how to add a custom n$suppress_for value for a notice through a policy
hook. While both scripts include an @load directive, it is left out in
RST document so as to avoid confusion.
