rework pluralisation mechanism

[kristofsajdak]

Currently Harvest uses inflect to transform a singular noun into a plural
which can be awkward at times : e.g. trackingDatum

[ssebro]

I think a bigger issue is that sometimes you may pick a noun that has unclear singular/plural forms, e.g. data. Data is both plural and singular, and datum is also a singular version of data - both are correct. So trackingData is fine, and the plural of trackingData is trackingData, HOWEVER, the singular of trackingData (re:inflect), is trackingDatum. We should include a bit of code in harvest that ensures that all names can be reliably converted back and forth, from singular to plural to back again.