Allow Release and Target to be set in Gruntfile

This change adds to more configuration options that can be set in the Gruntfile.  Both of these were necessary for my current project.

In the options you can set target, which is then passed to the RPM for the target architecture (noarch, x86_64, etc).  If the value isn't set, it defaults to noarch, the current value and what seems like the safest approach.

Also in options you can set the value of release.  Before this change, regardless of the value passed the release was always 1.  This doesn't play particularly well with installing the RPMs since RPM would think it was already installed.  This change keeps the backward intention -- if the value was set to boolean true then the value is 1.  If the value is set but isn't boolean true then the value of the release will be used.  If the value isn't set at all then the default of SNAPSHOT and timestamp is used.