Move to beginning and end of lines uses screen lines

* Open a file with long lines
* Soft wrap 
* Hit end at the beginning of a long line

It moves to the end of the buffer line. Super frustrating. 

So the select to the end/beginning, and delete to end/beginning both use screen lines, but this uses buffer lines.

This pull removes the beginning / end of screenlines commands and moves the canonical commands to use screen lines. 
`editor:move-to-end-of-screen-line` has keybindings associated with it [1](https://github.com/atom/atom/blob/master/keymaps/darwin.cson#L118) [2](https://github.com/atom/atom/blob/master/keymaps/base.cson#L4).

Isssue #1123 is why we have `editor:move-to-end-of-line` and `editor:move-to-end-of-screen-line`