Release version 2.3.0

Major features:
* Use case scenarios: To simplify the user interface, question types and
  functions are now enabled on a per session basis. Unused features are
  hidden and no longer distract from the workflow.
* Improved UI theming: Theming has been simplified by providing a
  variables file. Deep knowledge of CSS, SCSS and ARSnova's HTML
  structure is no longer required for color adjustments. Additionally,
  the default theme got a refresh.
* Message of the Day: It is now possible to display a message to all
  users per session or globally.
* New question type "Ask the audience": four options A, B, C, and D
  without question text.
* CSV export/import (experimental): Questions and their answers can now
  be exported to a simple CSV file.

Minor features and changes:
* Improved formatting: New formatting options (GitHub Flavored Markdown)
  are available.
* New templates for opinion polls have been added.
* Chrome's "pull-to-refresh" action is now longer triggered in text
  fields.
* Text selection in multiline editors no longer triggers scrolling.
* It is now possible to freeze live feedback.
* Image uploads except for hot spot questions and image answers are no
  longer available. Images on external servers can still be embedded via
  Markdown.
* Usability improvements and bug fixes

Bug fixes:
* Image scaling and rotation have been fixed.

Changes for developers:
* The `grunt run` build task has been improved to display important
  messages by Sencha Cmd. Verbose output for debugging purposes is
  displayed when parameter `-v` is used.
* Maven builds are now deprecated for the frontend. Please use Grunt
  instead.
* Version information is now saved with builds and is accessible via
  `Version` controller.

**This version is brought to you by:**
Project management: Klaus Quibeldey-Cirkel
Lead programming: Andreas Gärtner, Daniel Gerhardt, Tom "tekay" Käsler,
Christoph Thelen
Contributions: Daniel Haag (University of Innsbruck), Juan Markowich,
Marco Schäfer
This tag has no release notes.