Description of problem:
setcap should have an option for removing any records regarding to capabilities.

Steps to Reproduce:
# getcap foo
# 
# setcap cap_chown+ep foo
# getcap foo
foo = cap_chown+ep
# setcap all= foo (or setcap all-epi foo, setcap = foo)
# getcap foo
foo =

Actual results:
# getcap foo
foo =

Expected results:
# getcap foo
#