Use Tomcat's compression instead of Atlassian GzipFilter

Atlassian GzipFilter duplicates functionality in Tomcat, for allowing clients to opt in to a compressed response. Remove it and configure Tomcat to use compression.

This is partially motivated by problems when upgrading to Tomcat 8; the simplification seems like an improvement as well.

As part of this change, the Crowd console will lose the ability to configure compression. However, the only value of that setting is to allow Crowd to ignore a client's request for a compressed response. That seems like an unlikely enough case that a (simple) change to the Tomcat configuration is an acceptable workaround.