initial work_package#index implementation

Only implements index within projects for now
lets query saving redirect back to work_packages controller
separates query results from the query itself
enables csv export for work packages#index
enables pdf export for work_package#index
enables atom feed for work_packages#index
error handling work_packages#index
prevent unauthorized export
fixes work package pagination cuke
fixes work package cuke links
corrects automated work package update text
removes issues#index action
enables the atom feed on work_packages#show