limit queries

limit the number of queries per ip per day, default is 3, configurable in web.xml, effective immediately (no need to restart tomcat).
files added: 
* queryexceeded.html
* SimpleQueryLimitFilter.java
files updated:
* web.xml


Do we actually need it though? I don't see why we would want to stop people from submitting the same query multiple times when we could easily just block them when they reach the limit.