Developer documentation improved

docs/source/developer/project_structure.rst

@@ -0,0 +1,25 @@
+This project is structured into several folders as shown below. The three main folders are ``docs``, which contains the documentation,
+``esbo_etc`` containing all source files and ``tests``, where all tests are located.
+
+::
+
+    root
+    ├── docs                        Documentation files
+    │   └── source                  Source files of the documentation
+    │       ├── configuration       Configuration chapter of the documentation
+    │       ├── developer           Developer chapter of the documentation
+    │       └── usage               Usage chapter of the documentation
+    ├── esbo_etc                    Source code of ESBO-ETC
+    │   ├── classes                 Contains all classes of the source code
+    │   │   ├── optical_component   Contains all class files of the optical components
+    │   │   ├── psf                 Contains all class files to model the different types of PSF
+    │   │   ├── sensor              Contains all class files of the sensors
+    │   │   └── target              Contains all class files of the targets
+    │   ├── lib                     Contains all library functions
+    │   └── esbo-etc.py             This is the main file to run the application
+    └──  tests                      Contains all tests
+        ├── data                    Necessary data for all tests
+        ├── optical_component       Tests of the optical components
+        ├── psf                     Tests of the different PSF implementations
+        ├── sensor                  Tests of all sensors
+        └── target                  Tests of all targets