Allow admin paths to be set at server scope.
Merge pull request #701 from pagespeed/jefftk-move-settings-to-server-scope

move settings to server scope

Allow you to set `MessagesPath`, `StatisticsPath`, `AdminPath`, or `ConsolePath`  in a `server {}` block.
Merge remote-tracking branch 'origin/trunk-tracking' into matterbury-sticky-options

if it merges an updated upstream into a topic branch.
Added system test for sticky options.