Jetty 6 package.

- Add several jars from the Jetty 6 distribution
- Update jetty.xml
- Add context XML files
- Update WorkingDir to migrate the content XML files
- Update RouterConsoleRunner and LocaleWebAppHandler
- Remove all old Jetty 5.1.15 local mods;
  this will break Seedless using a custom Server() constructor
- Update I2PRequestLog to be a mod of NCSARequestLog from 6.1.26
- Put I2PRequestLog in its own jar
- Copy MultiPartRequest and other required classes from Jetty 5.1.15
  and add it to susimail, as the replacement MultiPartFilter in
  Jetty 6 is difficult to migrate to, and does not support content-type
- Update i2psnark for Jetty 6
- Disable i2psnark RunStandalone, unused and instantiated Jetty 5
- Fix up all webapp build.xml to reference new jars

Not yet working: Plugin/webapp run detection and stopping, eepsite CGI
Not well tested: Plugins, classpaths, webapps