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
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
use Pathname ruby api in plugin so relative paths are resolved better
fix paths and links so that guide/ subdir build works nicely
ensure host is included when needed
tidy up config.yml comments, and set encoding utf-8 so accents etc work
new build script which can write docs to root, to /guide, or to /v/VERSION
add website files, and update the build.sh script appropriately
install javadoc to the right place