BROOKLYN-101: avoid recordLocationEvent on rebind

- Previously on rebind we would call recordLocationEvent, which would
  try to get `inferMachineDetails` over ssh in the rebind thread
  (taking a long time).
- Now we don’t recordLocationEvent or recordApplicationEvent on
  startup or shutdown.
Tests for catalog items versioning functionality.
Adds AttributeSensor.persistenceMode

- If set to NONE then that attribute’s value will not be persisted, so will
  not be available on rebind.
- Adds Sensors.builder() to avoid too much overloading.
BROOKLYN-102: Fix MongoDB rebind

- Declare STATUS_BSON as transient, so won’t be persisted
  (because that value failed to rebind)
This closes #397
Fixes issue that was causing MongoDBServer to restart after being stopped
Adds missing call to super.connectSensors() to BindDnsServerImpl
This closes #401
Support logging VM credentials

- In JcloudsLocation, if config says so then log the password/privateKey
- Useful for when debugging failing to ssh (e.g. in vcloud-director!), 
  but config should never be used in production!
RebindOptions (in tests): make public

- Let RebindOptions be used in downstream projects
Adds YamlLauncher.launchAppYaml(Reader) for tests
Add tests for Postgres restart/rebind

- And changes Postgres connectSensors() to use
  connectServiceUpIsRunning(), given that was all
  the feed was doing anyway.
Add MongoDBRestartIntegrationTest
rename layout to guide-normal
move tests and build things to _build
move deps to deps dir; and upgrade to jquery 2.1.1 (as used in main website) and install bootstrap (also used for main website)
restructure css and images for guide (versioned files) to align with main website
add bootstrap fonts, and point to subdir of deps for clean isolation
add underscore libs used by main website (in prep for import)
move version-specific things to "guide"

"guide" is where versioned content will live when primary website is moved in (to "website" dir);
note this does not yet build; update fixing that to follow