add jetty maven plugin to pom.xml
can now run project with mvn jetty:run,
and keep editing files in the meantime without redeploying
fix #48 : removed source IP check for all requests
There used to be only 1 client IP authorized to make requests
using a session. this made the application unusable for clients
that are connecting to the server using multiple IPs (ie for load balancing).

Also, each user can now create multiple concurrent sessions.
Logging in does not remove sessions anymore.
This allows logging in from different locations (ie home and work).