Nullary functions not accepted by parser

[xiao-cheng]

Currently SQL functions such as random() that has zero arguments are not accepted using deepdive compile.

Here is Jaeho's note:

Actually, I took a brief look at ddlog compiler code, and it turns out if you modify one byte in ddlog source, random() will probably be accepted: changing rep1sep to repsep at: https://github.com/HazyResearch/ddlog/blob/master/src/main/scala/org/deepdive/ddlog/DeepDiveLogParser.scala#L240