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
pin: Fix the template.

In APT preferences files the only allowed comments are lines that start
with `Explanation:`, commented lines that start with a # trigger a
myriad of interesting bugs. This is considered a feature of APT.

Because we're only ever writing a single file at a time with only a #
comment at the top we were getting away with this but it shouldn't be
there in the first place.
pin: caller_module_name is not a topscope variable
unattended-upgrades: Fix origins for Squeeze.

Because Squeeze is now oldstable we need to add an oldstable line too
otherwise security updates won't be picked up. This is still because we
can't match on codename.
Merge pull request #281 from daenney/unattended-upgrades-squeeze-origins

unattended-upgrades: Fix origins for Squeeze.
Merge pull request #280 from daenney/fix-pin-comments

Fix pin comments
Add security warning re: short keys
Merge pull request #282 from laurenrother/security

Add security warning re: short keys
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