Revert "Fix for sessions with taken attendance show twice in student report."

This reverts commit 5bddb944c0b912ef3f0bc74ff3d99dfae3be1300.
Duplicate fix that will work on MSSQL
Merge pull request #11 from NeillM/fix_MSSQL_issue

Fix mssql issue
Fixed validation rule for multiple sessions that end date must be after start date
Merge pull request #12 from tlock/master

Fixed validation rule for multiple sessions that end date must be after ...
On upgrade, update grade items to 'attendance'
Merge pull request #13 from tlock/master

On upgrade, update grade items to 'attendance'
Fix capability upgrade issues for Attendance
Merge pull request #15 from tlock/master

Fix capability upgrade issues for Attendance
Show Common groups always
Merge pull request #16 from tlock/master

Show Common groups always
Fix missing language strings and enable groupings

Fix missing language strings and enable groupings and
enablegroupmembersonly. Most places already support groupings.
Merge pull request #17 from cedict/master

Fix missing language strings and enable groupings
Added Russian Translation

Added translation of module into Russian language
add missing grade_items_history upgrade step
use cross-db update of capabilities
CONTRIB-4754 Added upgrade step to account for name change from
"attforblock" to "attendance":
- updated itemmodule field in the grade tables
- updated role_capabilities table to preserve old capabilities
- deleted old data from capabilities and role_capabilities tables
bump version to release to plugins db
Changed deprecated get_context_instance to context_module::instance
Added Russian translation to AMOS