Does filters support comparison of negative numbers?

[naveen-vardhi-glean]

Grammar at lib/sisyphus-dsl/src/main/antlr/com/bybutter/sisyphus/dsl/filtering/grammar/Filter.g4 doesn't support negative values.

I have modified it to following

value
    : sign='-'? tok=NUM_INT duration='s'?    # Int
    | sign='-'? tok=NUM_FLOAT  duration='s'? # Double

Let me know if this looks good and I can send a PR for the same.