#189 introduced row/col naming uniformity in frame API
Remove test code from Deedle.fsx and minor documentation tweak
Fix documentation for expanding functions according to https://github.com/BlueMountainCapital/Deedle/issues/185#issuecomment-39250612
Improve Frame.stack and correctly infer type of values (fix #192)

The bug #192 was caused by the fact that Frame.stack returned values as
a column of type 'obj' and so the expansion based on the static type of the
vector did not work. We could change expansion, but I think it is better to
make sure that static types are propagated correctly (this also makes things
work better with R - as the added test shows).

I did some minor improvements to how we infer types from values (which is
also used when reading data from R data frames) and used this to implement
`Frame.stack`. I also did some performance tweaks, so `Frame.stcack` is now
~4x faster on a frame 1000x1000.
Adding Stats.levelFoo functions (close #185)

The "level" functions are just simple shortcuts for that call `applyLevel` under
the cover, but they might be handy for quick interactive explorations.

Aside from adding the functions, I also cleaned up the documentation a bit.
Merge series/column renaming changes
WIP: More cleanup - Series and Stats naming and documentation

I update F# Formatting and added github source links to the generated documentation &
did various tweaks in the Series and Stats module documentation (there are still pieces
missing, but it looks pretty good and well organized now).

I finished renaming (#179) and renamed `Series.union` and `Series.append` to
`Series.merge`. I also used `mergeAll` instead of `mergeN`, because I think the
name "all" appears in multiple places of the API (so it is more consistent than
using "N").

Finally, I moved two last statistics-related functions `Series.minBy` and `maxBy` to
the `Stats` module. I also deleted the obsolete functions - we probably want to handle
compatibility better after the next release, but since we are renaming so many things,
I think there is no point having _some_ obsolete functions but not _all_.
Do more renaming ("series" and "column") (c.f. #189)

I found a few more occurrences of "series" and replaced them with
"column" to finish the idea in PR #190.

There was another minor inconsistency where we sometimes used
`cols` and sometimes `columns` in the F# API, so this changes
everything (in the F# module only) to use `cols`. I would be equally
happy with `columns` though (I just picked the more common one).
Merge changes from GH185-renaming
Merge remote-tracking branch 'tomas/mainline' into mainline

* tomas/mainline:
  Do more renaming ("series" and "column") (c.f. #189)
  WIP: More cleanup - Series and Stats naming and documentation
  Merge series/column renaming changes
  Adding Stats.levelFoo functions (close #185)
  Improve Frame.stack and correctly infer type of values (fix #192)
  Fix documentation for expanding functions according to https://github.com/BlueMountainCapital/Deedle/issues/185#issuecomment-39250612
  Remove test code from Deedle.fsx and minor documentation tweak
  #189 introduced row/col naming uniformity in frame API
Start correcting tests and renames for #196