rfe #1564 Improve action message on Tracking page

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Database column is redundant

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Add @return doc comment

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Allow deleting individual versions of tracking data

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Improve action message

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Merge branch 'tracking'