Update NetworkChecker to match dev_4_4
Refactor connectors to multimap
Remove synchronized from isSessionAlive
Add caching to Connector

Connector objects were being created without needed
in some instances. Since the instantiation of an
omero.clients object has high overhead, it's worth
preventing this.
Add static caching to NetworkChecker

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/util/NetworkChecker.java
Remove ping since it doesn't check entryUnecrypted
Refactor isSessionAlive/network logic into getConnector

Since all service access calls getConnector(), all logic for
handling the checking of alive sessions and network has been
refactored into the one location. This also prevents multiple
calls.
Fix race condition on UserDetails

Most likely, the synchronized methods on OMEROGateway
were hiding this, but a race-condition during startup
allowed dsFactory.getCredentials() to return null.
Increase keep alive check to 30 seconds
Use cached Connector!
Remove all synchronization from OMEROGateway methods