Clean up logfiles

The logs generated by the website contain a gazillion lines like these:

WARNING [http-apr-8080-exec-2] org.apache.commons.httpclient.HttpMethodBase.getResponseBody Going to buffer response body of large or unknown size. Using getResponseBodyAsStream instead is recommended.

as well as:

com.opensymphony.oscache.web.filter.CacheFilter.doFilter <cache>: filter in scope 4
com.opensymphony.oscache.web.filter.CacheFilter.doFilter <cache>: New cache entry, cache stale or cache scope flushed for /images/ignite_blog_icon_comment_sm.gif_GET_

These are very uninteresting, and add a lot of noise in between which the interesting stuff gets lost. Lets prevent these lines from being logged.