Added automatic migration of old event subscription format to the new one
(cherry picked from commit e7088ef)
Modified versioneer to allow specification of manual versions based on branches

You can now define a lookup file explicitely mapping virtual version tags to branches via regular expressions and a reference commit from which the commit distance will be calculated.

Format of the file is

  <branch-regex> <tag> <reference commit>

The file is processed from top to bottom, the first matching line wins. If <tag> or <reference commit> are left out, the lookup table does not apply to the matched branches and the regular versioneer resolution (via git describe) takes place.

Current configuration makes "master", "staging" and any branch starting with "fix/" make use the default behaviour, all other branches (so basically all development branches) are defined as "1.2.0-dev"
(cherry picked from commit 212f40c)
Versioneer now also returns and persists the branch from which OctoPrint was installed

Changed version output accordingly to now display "{version} ({branch} branch)" if branch information is available (which should be the case if installation was performed from git).
(cherry picked from commit a48b5de)
Renamed RELEASE-NOTES.md to CHANGELOG.md, added note regarding new version format
Merge branch 'master' into devel

Conflicts:
	src/octoprint/events.py
	src/octoprint/server/__init__.py
	src/octoprint/settings.py
	src/octoprint/templates/index.jinja2
i18n: Added dutch and norwegian translations
Some more entries into the Changelog, trying to get up to date...
First experiments with a plugin system, service discovery and connectivity ensurance
discovery plugin: removed _workstation._tcp registration, added more parameters to http and octoprint txt records
discovery plugin: let's try upnp
Use netifaces for ipaddress iteration
Fixed error in usage of netifaces
Forgot to commit template files
Fixed a typo in an URL
Also forgot to add knockout mapping plugin to git
discovery now has automatic location url building based on querying client
Added shutdown trigger and UUID persistence
Also install plugins from setup.py and don't log notify as info level
Better logging for NOTIFY messages
Integrated netconnectd plugin with netconnectd service