add some simple test case for coalesce expression
refactor test cases and add more interesting cases
make lines no longer than 105 char
change one line comment
Merge branch 'master' into ENG-6552-COALESCE-function
move test case to TestFunctionsSuite and use case when instead of decode
Merge branch 'master' into ENG-6552-COALESCE-function
use another sql query to test coalesce(null,null,null)
Merge pull request #1505 from VoltDB/ENG-6552-COALESCE-function

Eng 6552 coalesce function test cases