[artifactory-release] Release version 1.8.1
Update release version to 1.8.2-SNAPSHOT
Add previewURL to LightweightAssetRepr

This will be populated in the asset search resource and will contain a
permanent external link to the display preview image. Returning
externally accessible links is not necessarily good API practice but
in this case it follows the behaviour of thumbnailURL.

Required for AB-1796
Merge remote-tracking branch 'origin/AB-1796'

Conflicts:
	pom.xml
	src/main/java/com/brightinteractive/assetbank/restapi/representations/LightweightAssetRepr.java