Automatic merge of T1.5.1-799-gb02a6e5d3 and 14 pull requests

- Pull request #570 at 3539862: Experimental glTF 2.0 support with PBR lighting
- Pull request #839 at d00beb9: First phase of https://blueprints.launchpad.net/or/+spec/additional-cruise-control-parameters
- Pull request #876 at f92de76: docs: add source for documents previously on website to source Documentation folder
- Pull request #882 at a055bca: Blueprint/train car operations UI window
- Pull request #885 at 8f94333: feat: Add notifications to Menu
- Pull request #886 at 6c0785b: Scene viewer extension to TrackViewer
- Pull request #892 at 1f5ba4c: Signal Function OPP_SIG_ID_TRAINPATH
- Pull request #896 at 5866028: First implementation of https://blueprints.launchpad.net/or/+spec/specific-sounds-for-ai-trains
- Pull request #897 at 42f1dd9: feat: Improved system information collection
- Pull request #899 at b48ac9f: Duplex steam engines - Booster Engine addition
- Pull request #903 at 9ba83fd: Downloading route content (Github, zip)
- Pull request #907 at 9b0b04f: Bug fix for https://bugs.launchpad.net/or/+bug/2047300 Dynamic tracks disappear after long tunnel
- Pull request #908 at 4b4afe3: feat: supports switching adhesion precisions
- Pull request #911 at 6834af0: docs: Add refactoring as a special type of PR

Author: openrails-bot

Source/Documentation/Manual/images/download-content-form.png

@@ -16,7 +16,24 @@ installation profile.
 
 .. image:: images/start-activity.png
 
-If not, then you must download some content and add it as an Installation Profile.
+If not, then the next ``Download Content`` form is shown where you can download content. This form is described in the next `Content` chapter.
+
+Content
+=======
+
+Clicking on the ``Content`` button makes the ``Download Content`` form popup (if not already there for an new empty Open Rails installation):
+
+.. image:: images/download-content-form.png
+
+Select the route to be installed. This list will be enlarged by the OR team when suitable routes become available.
+However it is still possible to install routes manually as described in the next chapter.
+
+* ``Install path`` and ``Browse``: Fill in or Browse to the path where the route is to be installed. Each route will be installed in it's own subdirectory.
+* ``Info``: Gives more information of the selected route. The default web browser will be started with the information page.
+* ``Install``: Installs the selected route. A popup mentions the directory where the route is to be installed before starting the actual install. Installation profile gets added also.
+* ``Start``: Some routes have default start parameters and can be started via this button with these parameters.
+* ``Delete``: Delete route with this button. Take care: whole directory including added and changed files gets deleted.
+* ``Update``: GitHub based routes can get updated after the install by means of this button. Check for updates is done when clicking this button. Or at the end of the information webpage. Also GitHub has a watch possibility for getting changes on the repository being mailed.
 
 Installation Profiles
 =====================