Odd reference syntax

[afscrome]

The following is valid in NVelocity, but looks like it should be a syntax error. This is causing problems with the Antlr based parser. Investigate / decide whether this is a bug in nvelocity, and if we should maintain backwards comparability.

#set($x = 123)
#set($y = $$x)
#set($z = #$x)

$x || $y ||$z

Expected: 123 ||  ||  
Actual:   123 || 123 || 123

[afscrome]

This could be quite difficult to fix. Currently with the ANTLR parser, References are parsed the same way in text & argument modes. However with nvelocity, the textual string #$x is treated as a textual # followed by $x. That means we'd need different handling in the parser for references between. Won't fix.