Updated build.gradle to use maven.netkernelroc.org so that no local
NK maven server is needed.  Loosened the versioning in the compile
dependencies.
Fixed installNKSE task - wrong version in the jar install.  Still to
do: normalize version using property in NetKernelPlugin
Added NKEE download, fixed NKSE/NKEE install exec
Parameterized the NKEE download process