Add instruction how to install ArmarX Python via axii.

Currently, only the poetry-version of python is documented.

docs/installation.rst

 Installation
 ============
 
+You may install the ArmarX Python either as a pypi package, or from source. When installing from source, which guarantees you to use the most up-to-date version of the code and enables you to contribute to the development of the ArmarX Python code itself, you can choose between a manual installation and an automated installation via axii.
+
+Option 1: Installation via PyPi Packages:
+-----------------------------------------
+
 The ArmarX Python bindings are available as packages.
 Just grab the latest version from `pypi.org <https://pypi.org/armarx>`__ .
 
 With poetry 
 
 .. highlight:: bash
 .. code-block:: bash
 
     poetry add armarx
 
 or with pip
 
 .. highlight:: bash
 .. code-block:: bash
@@ -21,7+26,7 @@
 
 Alternatatively, you can create a project template with the `armarx-package`
 tool, i.e. `armarx-package add python <your project name>`.  Then you can use
 `poetry install` to setup a virtual env.
 
 
 Since the `zeroc-ice` package requires a rebuild you can grab already precompiled packages
@@ -45,7+50,7 @@
     url = "https://pypi.humanoids.kit.edu/simple/"
 
 
+Option 2: Installation From Source, Manually
+--------------------------------------------
+
+Clone the ArmarX Python repository somewhere. If you are in an active axii workspace, executing `echo $armarx__python3_armarx__PATH` might return a path that indicates where that repository is already cloned on your computer.
+
+Within the base directory of your ArmarX project, run
+
+.. highlight:: bash
+.. code-block:: bash
+
+    armarx-package add python subfolder-name
+
+This creates a pyproject.toml at `python/subfolder-name/`, from which you can delete the armarx-dev dependency and the pypi.humanoids.kit.edu repository.
+
+Still being in `python/subfolder-name/`, create a virtual environment by running
+
+.. highlight:: bash
+.. code-block:: bash
+
+    virtualenv venv
+
+Update pip by running
+
+.. highlight:: bash
+.. code-block:: bash
+
+    source venv/bin/activate
+    pip install --upgrade pip
+
+Now you can install the dependencies of your python project, by running
+
+.. highlight:: bash
+.. code-block:: bash
+
+    pip install pyproject.toml
+    pip install -e path/to/the/armarx-python/repository
+
+
+Option 3: Installation From Source, via axii
+--------------------------------------------
+
+Create an axii module for your project. Below, you can find a short example. For an extensive documentation, visit https://git.h2t.iar.kit.edu/sw/armarx/meta/axii/-/blob/main/docs/module_authors/README.md.
+
+.. highlight:: json
+.. code-block:: json
+
+    {
+      "general": {
+        "url": "https://git.h2t.iar.kit.edu/path-to-your-project",
+        "authors": [
+          "FirstName LastName <mail@example.com>"
+        ]
+      },
+    
+      "update": {
+        "git": {
+      "h2t_gitlab_slug": "path-to-your-project"
+        }
+      },
+    
+      "prepare": {
+        "cmake": {
+          "definitions": {
+            "CMAKE_C_COMPILER": "$ARMARX_C_COMPILER",
+            "CMAKE_CXX_COMPILER": "$ARMARX_CXX_COMPILER"
+          }
+        },
+        "python": {
+          "packages": {
+            "python/folder_of_your_python_project_in_which_to_create_a_venv": {
+              "install_editable": [
+                "$armarx__python3_armarx__PATH"
+              ]
+            }
+          }
+        }
+      },
+    
+      "build": "cmake",
+    
+      "required_modules": {
+        "tools/default_python_interpreter": {},
+    
+        "armarx/meta/compiler": {},
+        "armarx/python3-armarx": {},
+        "optionally/add/further/packages/just/as/armarx/VisionX": {}
+      }
+    }
+
+Add the axii package to your workspace and upgrade your workspace as usual (see https://git.h2t.iar.kit.edu/sw/armarx/meta/axii). This will automatically create the virtual environment and setup ArmarX Python.
+
+
 
 Configuration
 -------------