Fix null reference exception in AcceptAndValidate
Ignore built zip file
Add switch to build Chocolatey package
Add Remove-PSReadlineKeyHandler

Sometimes you just don't want a key binding for whatever reason, so now you can remove a binding.

Note that unbound keys won't fall back to what happens in "cooked" editing mode.
In raw editing mode (which is what PSReadline uses), conhost only handles a very small
set of key bindings and those bindings weren't available to PSReadline anyway.

Fixes #154
Raise PowerShell.OnIdle if needed

If there are any registered handlers for the engine event PowerShell.OnIdle,
raise the event that PowerShell would have raised so the event handler
can do it's work.

Fixes #169
ClearScreen now clears the screen, not the buffer

ClearScreen is meant to just clear the screen, not the full buffer.
The command cls (or Clear-host) will clear the full buffer.
Add bindings to scroll the screen up/down by line

New functions:

    ScrollDisplayUpLine
    ScrollDisplayDownLine

And corresponding key bindings Ctrl+PageUp/Ctrl+PageDown

These functions accept a numeric argument, but the DigitArgument
implementation isn't compatible with scrolling the screen, so
it's not that useful unless a custom binding wants to do
something interesting, like scroll half a screen.
Merge branch 'master' of https://github.com/lzybkr/PSReadLine

Conflicts:
	PSReadLine/Changes.txt