(#15981) confine/suitability is now late-binding

Since #6907, confines for providers have been late-binding.  #14822 makes
feature confines the same, so docs should recommend these over expressions.
(#11396) Namespace references to $operatingsystem

These examples refer to a Facter variable and should specify the empty
namespace in order to comply with section 11.6
(#11396) Break out examples for 11.6

Break the examples out into two code blocks so that it matches the style of
the other sections and is easier to read.
2.7: note that reserved words can't be used as resource attribute names.
update old language guide w/ version number for unless statements
Dupe 2.7 reference manual for 3.0 release
PRM3: Easy version number updates

These changes require little judgment, and largely just update references that
are still valid.
PRM3: Include arrays, CR escapes, reserved words in attributes, report format 3

Update descriptions of several small features added to 3.0.
PRM3: "Unless" statements

New syntax added.
prm3: seed TODO tokens for larger updates
ENC environments win, starting with puppet 3

This commit updates the external_nodes guide.
The old multi-binaries were removed for puppet 3

Update the table in the tools guide.
Update supported platforms for 3.0

- Ruby 1.8.5 got dropped
- Mac OS X 10.4 got dropped
As of 3.0, `puppet` no longer defaults to puppet apply
ENC changes: Edit environment.markdown and rest_auth_conf.markdown

- Add new default node ACL to auth.conf example
- Change environment docs to state that ENC environments now win
Adding Release Notes to provide a single source of truth and link base for breaking changes.
Initial writing and editing of Release Notes page.
Further edits and writing of 3.0 release notes.
Further writing and edits to release_notes. Completed "changes to dependencies" and "removed functions" sections.
Un-capitalize must/should/etc in ENC guide

Those allcaps advisories look extremely weird unless you're specifically
citing the relevant RFC, and are not strictly necessary in any case.