Several improvements & fixes

- "extract-y" was incorrect ("if" macro used as if/else without else), fixed using "cond" 
- shortened "produce-y" by making use of "select-fields" (https://github.com/nathanmarz/cascalog/wiki/Methods-for-handling-wide-sources)
- changed "produce-A" to be schema-independent. The whole text line is now fed with "lfs-textline" and converted into an array of integers, so this method can now be used with any input file consisting of a list of integers, no matter the size. And the explicit definition of the source is not needed anymore so I commented out "source-A" entirely.
- commented out some unneeded code, but more needs to be commented / removed.