#127 Add refactored procedures & fixes to migrations

db/migrations/V11_3__may's_fixes.sql

+delete from `study_groups` WHERE GradeID in (
+  select id from grades where Degree not in ('bachelor', 'specialist', 'master')
+);
+delete from grades where Degree not in ('bachelor', 'specialist', 'master');
+
+-- recalculate CurRate in discipline table
+update disciplines
+  inner join (
+               select  modules.DisciplineID, SUM(submodules.MaxRate) as rate
+               from submodules
+                 inner join modules on submodules.ModuleID = modules.ID
+               where submodules.isUsed and (modules.Type = 'regular' or (modules.Type = 'exam' and modules.OrderNum = 1))
+               group by modules.DisciplineID
+             ) as t on disciplines.ID = t.DisciplineID
+set disciplines.CurRate = t.rate;