RFR: 8196783: Refactor LogTagLevelExpression into separate classes

[Marcus Larsson]

Hi,

Please review the following patch to split up LogTagLevelExpression into 
two separate classes: LogSelection and LogSelectionList.

Issue:
https://bugs.openjdk.java.net/browse/JDK-8196783

Webrev:
http://cr.openjdk.java.net/~mlarsson/8196783/webrev.00

Tested with hs-tier 1-2.

Thanks,
Marcus