Add "Release Notes/Known Bugs" to Changelogdds "Release Notes/Known Bugs" to Changelog, updates file format to markdown, standardizes the format of previous entries

Per a request to have initial release notes that specifically listed known issues for this PE 3.2 release, and barred by time constraints from automating a pull from open issues in JIRA, this commit adds a Release Note and Known Bug section to the Changelog for the imminent 3.2 release. As it will display on the Forge, updates file type to markdown and standardizes previous entries.
Merge pull request #255 from laurenrother/1.4.x

Add "Release Notes/Known Bugs" to Changelog
Prepare metadata for supported module release.
Merge pull request #253 from apenney/add-metadata

Prepare metadata for supported module release.
Prepare supported module 1.4.2
Merge pull request #256 from apenney/supported-142

Prepare supported module 1.4.2
Add back in missing fields to work around Puppet bug.
Merge pull request #257 from apenney/last-minute-fix-metadata

Add back in missing fields to work around Puppet bug.
Fix typo.

Group was incorrectly spelt, but because the file was absent this
should have resulted in a noop in practice.
Merge pull request #267 from apenney/fix-typo

Fix typo
Add security warning re: short keys

(cherry picked from commit d7da1cef383663bb2ecee3d8afa612aea74219f7)
Writing proxy configuration in apt.conf.d/01proxy.

This commit changes the proxy file name to be more consistent with other files
in `apt.conf.d`. The old file (`apt.conf.d/proxy`) is removed.

Tests has been updated.
Merge pull request #283 from johanfleury/master

Change proxy's configuration file to be consistent with other config files in apt.conf.d
Prepare metadata for supported module release.
(cherry picked from commit ab03a989df37df3660f0916519d0f78f7ab73a13)
Add back in missing fields to work around Puppet bug.
(cherry picked from commit dc472717163d30a4463f687a577238ec2539601c)
Merge pull request #285 from blkperl/fix_metadata

Fix metadata.json file
unattended_upgrades: Fix matching security archive

The default configuration we were writing for Debian was only working
for Squeeze, from Wheezy and onwards this wasn't working anymore. This
has to do with the fact that we should now be using Origins-Pattern
according to the unattended-upgrades docs. However, Ubuntu didn't
entirely get with the program yet...

This change reflects the defaults that unattended-upgrade installs on
every platform we support. In order to do so the unattended-upgrades
Debian archive for Squeeze, Wheezy, Lucid, Precise and Trusty were
downloaded and the default /etc/apt/apt.conf.d/50unattended-upgrades
checked for its content with regard to using Allow-Origins or
Origins-Pattern.

Fixes #277
Merge pull request #286 from apenney/fix-for-post-wheezy

unattended_upgrades: Fix matching security archive
Do not add bogus line to apt preference file on Debian Wheezy
Remove the preference file for all supported platforms when in purge mode