[request] limit axis and ranges on bones (especially for usages with transform constraints)

[bencresty]

When using a bone for transform constraints, like the pretty cool rigging setup for Squash & Stretch on the Esoteric Youtube (https://www.youtube.com/watch?v=w3gWQoUbSQo), we sometimes would like to restrict the possible directions and min/max translation for that bone.

Other times, when using rotating bones as a controller to control other bones, we'd like to set minimum and maximum angles for these controller bones to make these bones a little more 'fool proof' to use (never gets out of the allowed range).

(I personally never used bones' scaling to control other things and not sure if that's possible, but others might be?)

It would be nice if we, per bone, could at least:

• Lock x-axis for translation
• Lock y-axis for translation
• Set a local range (min/max) for x-axis translation
• Set a local range (min/max) for y-axis translation
• Set a local range (min/max) for the rotation

...to make controllers more dedicated to their purpose and less error prone for its use case (more fool proof so one could prepare a scene and another one (or the same person years later) gets all the controls with their possible ranges already set up and ready to go as intended.

For instance, when looking at the squash & stretch rigging, we would like to prevent things like this from happening, because obviously this rig is only meant to be controlled by moving the top bone up and down, not left and right, and not passing under the bottom bone:

https://user-images.githubusercontent.com/69322733/185191994-4bcc5848-ffe0-45a8-9c34-6dbbc5120b63.mp4