Improvements (Bugfixing + Functional Extensions)

BugFix: Refresh now really does a refresh to the reqPro database
Functional Extension: ContextMenu in Trace Graph to handle "Copy"
   and sync with TreeView
Refactoring: ReqTraceGraph Nodes handled in
   dedicated class --> moved from formMain
Feature Extensions

Feature Extension: Refresh on a per Package base in TreeView
Feature Extension: Hide/Unhide Columns in FormGeneric
   ("View Requirements", "View Log")
Feature Extension: Copy (to clipboard) TreeNodes per ContextMenu
Feature Extension: View Requirements out of the TreeNode per ContextMenu