top: provide an option to ignore configuration file(s)

While I initially rejected the issue cited below, upon
reflection I have decided to implement that provision.

The primary reason I changed my mind is because of the
potential presence of a global /etc/topdefaultrc file.

Unlike that /etc/toprc restrictions file, topdefaultrc
is intended as a courtesy to new top users. Instead of
forcing users to accept the build defaults, a sysadmin
could arrange for more suitable tailored top defaults.

Were that the case, using a symlink to top under a new
name would still yield such tailored results. In other
words there's no way to experience the build defaults.

Well, with these new short/long options there will be.

Reference(s):
#365



Signed-off-by: Jim Warner <james.warner@comcast.net>