rough sketch of json export tapExchange
factor out json mapper to separate package
implement exchange download url

but dont link to it yet
json download link for exchange
dont include content in exchange download
add jndi datasource to jetty

but don't use it yet
rename spring bean
pass datasource from container to webapp via jndi
let maven generate jetty-env.xml
clean up dependencies
base jetty-env on profile
delete jetty test runner

supposed to be started from mvn jetty:run now
let maven fitler tap-settings.properties
drop redundant 'database' in spring config
let maven set hibernate dialect
move log4j.properties outside war

expect log4j.properties to be provided on classpath
outside war so that logging can be changed without 
modifying the war.

A consequence is that we have two copies of log4j in the project,
one for jetty, one for junit testing.
maven target to start h2 console
dont start H2 console within webapp