Likely fix for print server deadlocks.

This pull requests updates the print-servlet jars to the latest on the 2.0.x branch.  

The update adds several resource leak fixes to mapfish print as well as a fix for a potential deadlock of the entire system in a very specific case where the output file is closed before a tile can be downloaded for the printing.

The change also adds a diagnostic API to the print server.  The path extension /metrics will provide access to the new API.

three new configuration options are also added:

- ignoreCapabilties - don't download the capabilities document for WMS and WMTS
- maxPrintTimeBeforeWarningInSeconds - Write to the log the spec for any print that takes longer than the specified time.  It is configured to 2 minutes
- printTimeoutMinutes - If a print takes longer than this time then cancel the print.  It is set to 5 minutes.