Nuvola Apps Runtime (Nuvola Player) 2.4.0

# Changes since version 2.3.0. Some fixes have already appeared in 2.3.x releases though.

Google Play Music:

 * Version increased to 4.11.

 * Removed broken Hide Google+ buttons feature, because Google changes the code too often.

 * Service settings are applied instantly without reload.

 * Fixed pause and toggle play/pause actions. (Closes: LP:1282346, LP:1321820)

 * Added warning about compatibility issue with desktop notifications for Chrome.
  (Closes: LP:1314753)

 * Added in-page navigation buttons. The buttons are inserted in the top bar next to the
   Google Play logo.

Rdio:

  * Version increased to 3.2.

  * Added in-page navigation buttons. The buttons are inserted in the top bar next to the rdio logo.
   (Closes: LP:1212167)

New services:

  * Logitech Media Server by Steffen Coenen. (Closes: LP:1010973)

  * This is my jam by Jan Vlnas. (Closes: LP:1310616)

User interface:

  * Implemented support for back/forward mouse buttons.

  * Fix support for actionable notification in GNOME lock screen. (Closes: LP:1305992)

  * Updated translations from Launchpad.

Stability:

  * Fixed many JavaScript crashes because of invalid JavaScript API objects. (Closes: LP:1263705)

  * Document viewer cache model of WebKit is no longer used, because it has been found to cause a
    huge memory usage. (Closes: LP:1275002)

Developers:

 * Implemented JavaScript API for user interface actions. It can be used to create associated custom
   in-page buttons for these actions. (Closes: LP:1265290)

 * Version of JSApi increased to to 2.3.

 * Added helper JavaScript functions to add and remove CSS stylesheets:
   Nuvola.addStyleSheet() and Nuvola.removeStyleSheet().

  * Tool to manage package database (package_db.py) recognizes JavaScript API 2.3.

  * Tool to create service packages (make_service_package.sh) got one new argument: path to service
    updates directory.

  * Tool to create service packages (make_service_package.sh) supports multiline changelog.

  * Unstable builds use user data and config directories with suffix "unstable".

  * Fixed build error with Vala compiler 0.24 (Closes: LP:1296261)

  * Added tool WebKitGtk Frame for debugging WebKitGtk compatibility.

  * Updated translation template