Feature request - Show percentage of unused fields

[moseleyi]

It would be useful to know the % of unused fields when looking at the output of analyze command:

+-------+------------+-------------+-------------------+-----------+------------------+------------+-------------------+-----------------+
| Model | Explore    | Is Hidden   | Has Description   |  # Joins  |  # Unused Joins  |  # Fields  |  # Unused Fields  | % Unused Fields |
|-------+------------+-------------+-------------------+-----------+------------------+------------+-------------------+-----------------|
| nodel | se_explore | False       | False             |     4     |        0         |    436     |        339        |     77.75%      |