This fixes unintentional duplications of words, such as `the the`, and
`can can` etc. I also take the chance to make a few wording tweaks to
avoid suspicious duplications.

We compile using the alwaysStrict flag so these directives are not needed.

This part removes most of the remaining use strict directives that were not caught by part 1 and 2

Tests for getSelectionSearchString: simple position, with simple selection and with multiline selection.