Feature Request: Ability to reset crew to minimum required

Environment

45.4
Windows
Java version 1.8.0_201

Description

When lowering the tonnage, the total crew does not decrease. (IE go from 100k to 500k back to 100k) due to the player being able to modify these values (#330).

However if the user then wants to set the crew back down to the minimum required they must either use the down arrow on each field until reaching the minimum, or lower the fields in increments until reaching the minimum.

If the user attempts to enter a number lower than the minimum, instead of being set to the minimum it jumps back to the current value.

It would be useful if we either had a button to reset all the crew values back to their minimum, or if you enter a number lower than the minimum, it is instead set to the minimum value.

Repo:

1. Create a blank Jumpship
2. Note the Total Crew: field count
3. Increase the Tonnage (+100k)
4. Note the Total Crew: field count
5. Decrease the Tonnage (-100k)
6. Try to set the base crew to 1 (so it would be automatically set to the minimum required)

Reproduce the issue in MegaMekLab with a blank Jumpship: increase and then decrease tonnage, then try setting base crew to 1. Start by locating the Jumpship tonnage and crew-field handling, and determine whether the accepted behavior is a reset control or minimum-value clamping. Done means crew values can return to their minimum required values after tonnage changes.