Refactor connectors to multimap

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OMEROGateway.java
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.

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OMEROGateway.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.

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OMEROGateway.java
Add static caching to NetworkChecker

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/util/NetworkChecker.java
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
Stateful service cleanup in env.data

 * Remove Connector.reconnect() since it leaves services dangling
 * Remove all get*Service() methods from OMEROGateway
 * Refactor all get*Service() methods in Connector
 * Use concurrent storage for services in Connector
 * Close all stateful services as quickly as possible.

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OMEROGateway.java
Fix concurrent modification err in Connector
Review loading of thumbnails. (see #10748)

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/agents/fsimporter/ImportResultLoader.java
Fix loading of thumbnails for bird eye view and fields (see #11071)
Do not set the default for the thumbnails.

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OMEROGateway.java
Remove commented out code.
Do not specify the user's ID.
Remove casting.
Create a thumbnail store.

Conflicts:
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OMEROGateway.java
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OmeroImageService.java
	components/insight/SRC/org/openmicroscopy/shoola/env/data/OmeroImageServiceImpl.java
Add support for multiple thumbnail loaders.