service.bat properly configures mem settings

service.bat converts X(m(s|x)|ss) to MB/KB and uses dedicated arguments to the underlying JVM DLL
empty/unset JAVA_OPTS no longer trips commons daemon
fixes #3785

(cherry picked from commit 971db7dd90262f1b3ce678be517fdabc933eb8bc)
remove unused setting

(cherry picked from commit ffe502ddc276f5485847e4816b86741c3c66c8fc)
remove unused class
Print Java Version during Validate
Add indexUUID to mapping-updated and mapping-refresh events and make sure they are applied to an index with same UUID.

This can go wrong if indices with the same name are repeatably created and deleted.

UUIDs can not be null anymore. If UUID is not available `_na_` will be used as a value.

Also - some minor clean up in ShardStateAction where shard started events could be added twice to the to-be-applied list where the second instance will be ignored.

Closes #3783
Returning useful exception when sorting on a completion field

Closes #3747
added a ToXContent implementation to NodeStats