Fixed 'sorted' event trigging for header cells with disabled sorting

Now sort event handlers added only for th's that was NOT disabled.
This fixes the case when user can trigger 'sorted' event for column with disabled sorting by simply clicking that th.
Fixed styles for header cells with disabled sorting
Merge pull request #26 from EugenyLoy/disabled_columns_soring_fix

Display and events handling fix for tables with sorting disabled for specific columns