add instance admin role

Rewritten-docs.md

@@ -1777,6 +1777,7 @@ Described roles are:
 - Student
 - Group supervisor
 - Group administrator
+- Instance administrator
 - Superadministrator
 
 ## Terminology
@@ -2168,6 +2169,13 @@ clicking on it some particular supervisor should not be supervisor of the group
 anymore.
 
 
+## Instance administrator
+
+@todo: who is this?
+
+@todo: creating groups right in the instance
+
+
 ## Superadministrator
 
 Superadmin is user with the most priviledges and as such superadmin should be
@@ -2214,7 +2222,11 @@ Roles description:
 
 ### Simple score calculation
 
-First implemented calculator is simple score calculator with test weights. This calculator just looks at the score of each test and put them together according to the test weights specified in assignment configuration. Resulting score is calculated as a sum of products of score and weight of each test divided by the sum of all weights. The algorithm in Python would look something like this:
+First implemented calculator is simple score calculator with test weights. This
+calculator just looks at the score of each test and put them together according
+to the test weights specified in assignment configuration. Resulting score is
+calculated as a sum of products of score and weight of each test divided by the
+sum of all weights. The algorithm in Python would look something like this:
 
 ```
 sum = 0