Updated Architecture (markdown)

Architecture.md

@@ -18,6 +18,7 @@
 - store files without duplicates
 - keep consistent state with main database
 - serve files to workers on demand
+- allow versioning of tasks with revert back feature
 
 To meet these requirements, **Storage** and **Database** must be set as bellow.
 
@@ -48,3 +49,6 @@ For user friendly access and modifying tasks following information should be sto
 - list of tasks with their newest version number
 - for every task and version list of used files (their hashed names)
 - for every hash name one human readable filename
+
+### Conclusion
+Files are internally stored by their `sha1sum` hashes, so it's easy to implement versioning and get rid of files with duplicity content. **Worker** also uses files by their hashes, which is great for local caching without worries about akctual version of given file. On the other hand, **Database** keep info about human readable names, so to users (teachers) are files presented in a friendly way.