workplane() should allow from tag as parameter, providing enhanced workplaneFromTagged() functionality

`workplane()` should be enhanced to include an optional `from `parameter which would specify a tagged workplane be used rather than the TOS face. `workplane()` functionality, including `offset`, would be able to be applied to copies of tagged workplanes. `workplaneFromTagged()` should be deprecated.
```python
.workplane(from="sometag", ...and all the other options...)
```
Example: A workplane is tagged.
```python
.faces(">Z").workplane().tag("the_tag")
```
Later you have a need to offset another workplane from that one, but you can't refer to the tagged plane, instead you have to duplicate the selection. That's a possible source of error and also doesn't say "now I'll make a plane offset from this other one".
```python
.faces(">Z").workplane(offset=-some_offset)
```
Wouldn't this be clearer?
```python
.workplane(name="the_tag", offset=-some_offset)
```

I have looked at the code, but I don't claim to fully understand possible risks of this enhancement.