Added entity dependencies.
Corrected Test cases.
Add postSave method in SensorInfo.
Corrected some more test cases.
UI test passing now.
Implement sensor plugin dependency calculation and optional default config entities to fix tests.
Added check for module existence due to an exception that is thrown when testing without 'node' module.
Merge branch 'fix-check-if-node-module-exists' of https://github.com/md-systems/monitoring into gsoc-plugin
Moved node dependent sensor to optional.
Improved Settings UI.
Generalize optional configuration to all modules.
Correction in Sensor UI.
Add Sensor UI for SensorEntityAggregator.
Eliminated constructor in MultigraphForm
Merge remote-tracking branch 'origin/gsoc-plugin' into introducing-multigraph