medical: refactor medical tools

[dastrukar]

less inheritance, more composition :] this should also allow more flexible implementations

Fixes #234 If you prefer that I remove UaS_MedicalTool entirely, since it's pretty barebones now, I don't mind moving all the stuff to the tools themselves

[caligari87]

I'll merge this in. If you feel like the base medical tool is redundant, I'll leave the refactor decision to you.