[CLEANUP] Rename Documentation/ to docs/ (#269)

This brings the project more in line with the default Symfony
project structure.

Author: oliverklee

README.md

@@ -53,9 +53,9 @@ this code.
 
 ## Structure
 
-* [class structure overview](Documentation/ClassStructure.md)
-* [graphic domain model](Documentation/DomainModel/DomainModel.svg) and
-  a [description of the domain entities](Documentation/DomainModel/Entities.md)
+* [class structure overview](docs/ClassStructure.md)
+* [graphic domain model](docs/DomainModel/DomainModel.svg) and
+  a [description of the domain entities](docs/DomainModel/Entities.md)
 
 
 ## Running the web server

Documentation/ClassStructure.md renamed to docs/ClassStructure.md

@@ -1,5 +1,5 @@
 // How to generate the SVG file:
-// dot -Tsvg -oDocumentation/DomainModel/DomainModel.svg Documentation/DomainModel/DomainModel.dot
+// dot -Tsvg -odocs/DomainModel/DomainModel.svg docs/DomainModel/DomainModel.dot
 digraph phpListDomainModel {
 
   //