Rework nrelease framework for pkgsrc. The way the bootstrap kit was

Rework nrelease framework for pkgsrc.  The way the bootstrap kit was
build was incorrect, since the wrong path names end up in the
binaries.  Instead of building it redundantly every time, just expect
a binary bootstrap kit.  Change the installer targets to be a conditional
instead (WITH_INSTALLER), but keep the old targets for compatibility.

The CGI frontend is temporarily removed until the configuration is
updated.  cvsup doesn't currently build, a workaround pkg will be added
latter.

Add a description of how this framework is intended to be used.