Move SmartStoreAdapter and tests out of Aura;
Modify Aura to allow for pluggability of external adapters;

Expose SizeEstimator.estimateSize via $A.util
Merge branch 'SmartStoreAdapterMove-squashed' of https://git.soma.salesforce.com/mobileplatform/aura into mobileplatform-SmartStoreAdapterMove-squashed
Merging origin/ravi/master-pending-moveOutSmartStoreAdapter into master