Tracking improvements. Implements rfe #1562

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Warn when no tables have been selected

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>
Merge pull request #1408 from madhuracj/tracking

Tracking improvements. Implements rfe #1562