Overhaul of quickstart documentation

Docs/build_linux.md

@@ -210,6 +210,11 @@ The above command will build the Python API for the system Python version. You c
 * Install the target Python version at the system level with the development headers and the distutils, replace *X* with the desired version:
 
 ```
+# The Deadsnakes PPA may be needed for some Python versions
+sudo add-apt-repository ppa:deadsnakes/ppa
+sudo apt update
+
+# Replace the X for the desired Python version
 sudo apt install python3.X python3.X-dev python3.X-distutils
 ```
 

Docs/ext_quickstart.md

@@ -0,0 +1,66 @@
+# Quickstart extras
+
+The following sections contain additional options and details for installing and running a packaged version of the CARLA simulator.
+
+* __[Command-line options](#command-line-options)__  
+* __[Config script](#config-script)__
+* __[Import additional assets](#import-additional-assets)__  
+
+---
+
+## Command-line options
+
+There are some configuration options available when launching CARLA and they can be used as follows:
+
+```sh
+    ./CarlaUE4.sh -carla-rpc-port=3000
+```
+
+* `--ros2` - Launch CARLA with the native ROS2 connector enabled
+* `-carla-rpc-port=N` - Listen for client connections at port `N`. Streaming port is set to `N+1` by default.  
+* `-carla-streaming-port=N` - Specify the port for sensor data streaming. Use 0 to get a random unused port. The second port will be automatically set to `N+1`.  
+* `-quality-level={Low,Epic}` - Change graphics quality level. Find out more in [rendering options](adv_rendering_options.md).  
+* __[List of Unreal Engine 4 command-line arguments][ue4clilink].__ - There are a lot of options provided by Unreal Engine however not all of these are available in CARLA.  
+
+[ue4clilink]: https://docs.unrealengine.com/en-US/Programming/Basics/CommandLineArguments
+
+--- 
+
+## Config script
+
+The script [`PythonAPI/util/config.py`][config] provides more configuration options and should be run when the server has been started:
+
+[config]: https://github.com/carla-simulator/carla/blob/master/PythonAPI/util/config.py
+
+```sh
+./config.py --no-rendering      # Disable rendering
+./config.py --map Town05        # Change map
+./config.py --weather ClearNoon # Change weather
+
+./config.py --help # Check all the available configuration options
+```
+
+---
+
+## Import additional assets 
+
+Each release has its own additional package of extra assets and maps. These are stored separately to reduce the size of the build, so they can only be imported after the main package has been installed. 
+
+__1.__ [Download](https://github.com/carla-simulator/carla/blob/master/Docs/download.md) the appropriate package for your desired version of CARLA.
+
+__2.__ Import the assets:
+
+* __On Linux__:
+Move the compressed archive to the _Import_ folder and run the following script to extract the contents:  
+
+```sh
+cd path/to/carla/root
+
+./ImportAssets.sh
+```
+
+* __On Windows__:
+
+    - Extract the contents directly in the root folder. 
+
+---