Custom serialization

[gluc]

Saving environments results in huge files. Instead of environments, we could simply save as list of list. Essentially, what we get when calling ToListExplicit

[dylanbeaudette]

I have an immediate use for this!

I was planning to include the data.tree representation of a very large taxonomy in the new SoilTaxonomy pacakge vs. de-normalized data.frame representation. The saved data.table objects are 10-100x larger than data.frame.

I would be happy to test this out.