Confirm custom command REQUEST #532

Syntax (and code) similar to System Command confirm. First commit,
please be gentle.
Merge branch 'Booli-confirmCustomCommand' into devel
Updated changelog
Update CHANGELOG.md
Enable API by default and automatically generate API key on first server startup
Don't use scare quotes when displaying the username.

See http://en.wikipedia.org/wiki/Scare_quotes for details.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Merge pull request #595 from koenkooi/scarequotes

Don't use scare quotes when displaying the username.
Started documenting plugin types and their API
Merge branch 'master' into devel

Conflicts:
	src/octoprint/settings.py
Merge remote-tracking branch 'origin/devel' into devel
Enable event subscriptions by default
Added changelog entry
Merge branch 'master' into devel
Improved slicing and file management

- File management is prepared to support folders (UI still lacking support)
- STL files are now first class citizens
  - can be managed via the file list (and filtered from it)
  - can be sliced on demand
- Slicing now happens via plugins
- Added Cura plugin
  - uses CuraEngine directly instead of full Cura installation
  - Cura profile importer for importing profiles from regular Cura installs via settings dialog
  - TODO: UI for editing profiles
- API for slicing and slicing profile management
Fix for deleting the file that is currently selected

Due to a missing switch to a refactored version of an internal data structure, that file stayed being selected but wasn't actually there anymore, leading to an error upon hitting Print.