logback.xml can now easily be added and/or overridden

    this creates a new brooklyn-logback-xml project which should be an optional dependency when you want default logging;
    and in the dist we have a conf/logback.xml explicit file with comments,
    and in tests we use the optional dependency with a note in a custom logback file

    this prevents the case where logback.xml was being pulled in from dependendencies (e.g. launcher)
    then even though we had an override logback.xml in the downstream project, logback was smart enough
    to find both and give warning messages
SshMachineLocation: avoid warnings about non-ssh flags
SshMachineLocation.copy: write to custom temp dir

- Changed to delete as soon as copied, and to set file permissions.
- Allow setting localTempDir on location
brooklyn web-apps don't use temp dir

- set temp-fir so doesn't expand into $tmpdir
SensorSummary: escape sensor name in URI

- Was getting exception when creating URI because customer-defined
  sensor had illegal chars in it
rest api: fix responseClass names
add logback as module so clean root builds work
include the file, rather than re-declare it, as per review comment
Convert entity code from groovy to java
Adding postgresql jdbc driver for testing
Adding postgresql entity and driver
Adding PostgreSQL integration test and adjusting MySQL integration test to share code
Simplifying after testing on various OSes
PostgreSQL work - addressing review comments
PostgreSQL work - adjusting PostgreSQL tests
Fixing database live tests to setup/teardown correctly
Fix failing SensorSummary when multi action:open

- Ensure don't register duplicate NamedActionWithUrl hints
- In SensorSummary, don't fail to build links if come across multiple
  "action:open" hints.
Fix failing (time-based) SensorRegistryTest
Adding dontRequireTtyForSudo for various OSes
AutoScalerPolicy: allow metric to be on other entity

- Instead of just monitoring the entity that the policy is associated
  with, allow a different entity to be supplied.