[yt-dev] Pre-YTEP: remove caching of datasets

[Matthew Turk]

Hi all,

Before I get too far into writing up a YTEP, I wanted to know if
anyone would object to disabling "caching" of datasets in-memory.

Right now, if you do:

ds1 = yt.load("something")
ds2 = yt.load("something")

"ds1 is ds2" will return True; this was done so that you could load a
dataset, then unpickle an object with a reference to that dataset, and
get the dataset back rather than a newly-loaded one.  But I think a)
folks don't pickle much b) it causes a lot of problems.  So I'm
wondering if it would be okay to just turn this off.

-Matt