better task_state description

Communication.md

@@ -49,6 +49,9 @@ Commands:
     - `state` - what is happening now. One of "DOWNLOADED" (submission successfuly fetched), "UPLOADED" (results are uploaded to fileserver), "STARTED" (evaluation started), "ENDED" (evaluation is finnished) and "TASK" (task state changed - see below)
     - `task_id` - only present for "TASK" state - identifier of task in current job
     - `task_state` - only present for "TASK" state - result of task evaluation. One of "COMPLETED", "FAILED" and "SKIPPED".
+        - COMPLETED - task was successfully executed without any error, subsequent task will be executed
+        - FAILED - task ended up with some error, subsequent task will be skipped
+        - SKIPPED - some of the previous dependencies failed to execute, so this task wont be executed at all
 
 
 ## Broker - Worker communication
@@ -194,6 +197,9 @@ Message JSON format is dictionary with keys:
 - **command** - type of progress. One of "STARTED" (evaluation started), "DOWNLOADED" (submission source downloaded), "TASK" (progress on one of the tasks), "UPLOADED" (results are uploaded), "ENDED" (evaluation ended)
 - **task_id** - id of currently evaluated task. Present only if **command** is "TASK".
 - **task_state** - state of task with id **task_id**. Present only if **command** is "TASK". Value is one of "COMPLETED", "FAILED" and "SKIPPED".
+    - COMPLETED - task was successfully executed without any error, subsequent task will be executed
+    - FAILED - task ended up with some error, subsequent task will be skipped
+    - SKIPPED - some of the previous dependencies failed to execute, so this task wont be executed at all
 
 
 ## Frontend - Browser communication