Specify configuration file in servlet init-parameters

[jalpedersen]

This patch allows one to specify the configuration file to use when C-L is running in a servlet-container.

[rnewson]

I definitely like the intent of the patch. There's at least one place that needs a fix, an InputStream is opened but not closed. Using init(ServletConfig) is obviously preferable to my constructor approach. I can get away with that only because I embed Jetty. Making C-L a pure WAR file with a jetty launch script would be a nice enhancement.

[jalpedersen]

Oops, committed a fix so the inputstream is closed. Making it a pure WAR file with a jetty launch script shouldn't be too much of a hassle as it's more or less the way I'm running it now.