allow indexname to be set without a value condition

Hello @x-ma, @nicks, 

Please review the following commits I made in branch 'giannic-indexname'.

8c678f06a4c1216d4b24f681b9745eb5da2b2a15 (2014-09-17 14:31:40 -0700)
allow indexname to be set without a value condition

R=@x-ma
R=@nicks
maybe `setIndexRangeKeyWithoutCondition`?