Implemented zero-arg version of `:echo`

Also added Vim ignores to .gitignore because I am that strange that I
was developing VsVim from within vanilla Vim. I did finish up in VS 2013
with R# and VsVim tho. :)
Made echo parse an expression after it
Evaluate the expression parsed after :echo
Errors should break key map processing

When an error is encountered processing a key which is a part of a key
mapping the remainder of the mapping should not be processed.  This is
documented in :help key-mapping, search for error.

closes #1435
First step to :echo &expandtab (echo option)

Plumbed enough of the "echo option" stuff through to get a unit test
working without breaking any others. The type inference of the F#
compiler seems to be a bit of a doozy.

I'm not entirely comfortable yet with what I had to do here. It seems to
me that VariableValue has been used in a both of places in which
Expression should have been used. Still, I will definitely need
@JaredPar to review this.
Fix end block parsing

Was only matching end elements which had letters only, need to match
letters and digits

closes #1439
Echo toggle/boolean options/settings

This is preliminary implementation. There are holes to be filled, and it
should probably be cleaned up some.
+ Only works for options which can be toggled; needs to be implemented
  for other option types
+ Doesn't handle window options, but once it does, there may be
  duplication between it and `RunSet`.
+ Does handle option abbreviations
+ Has some ugly nested matches
+ Definitely need to get Jared to review once I've matured it a bit
Fix build issue

Allows for build again on 2010 only.  Need to switch to some other
installs to verify the behavior
Added a better comment
Fix a deployment script issue
Fix AppVeyor issue
Merge pull request #1441 from jaredpar/fixes-build

Fixes build
Removed some unnecessary match statements

Simplified some of the complexity I had added in previous work by
replacing some of the unnecessary match statements I had added with
simpler code.

Also, reverted .gitignore to master state since I learned you can have a
global .gitignore.
Evaluate integer-valued options as expressions

Should a test for this be put elsewhere, instead of into the Echo suite?
I put it there because that is the feature I am working on. However, the
code that is in use is more general-purpose.
Evaluate string-values options as expressions

Same testing question as in last commit
Evaluable variables as expressions (and echo)
Evaluate window settings as expressions (and echo)
Added register info to command line

closes #1434
Fix a unit test failure
Extracted some methods from my spaghetti code

Tried to increase readability/maintainability by breaking down a large
method into smaller ones