Remove even more deprecated code

Even more for #8751.

I did a through scrub of the code base, looking for any pre-0.41 deprecated. I found what I was looking for. 
The following is removed with this PR, listed along side the commit they were deprecated with and the release that deprecation went into effect.

* `command/Commands.js` and `command/Menus.js`: Old export redirects (56ab3e942f5b651da6d91176cd4da8b41a8c7252, Sprint 39)
* `editor/Editor.js`: jQuery `triggerHandler` for `"keyEvent"` (21bea9d143825122b8b89528e84052c132b0c64a, Sprint 38)
* `search/QuickOpen.js`: Backwards compatibility for `addQuickOpenPlugin()` (1ec5c8f8c70dc4aed5e98e3254904a2e8a55ae48, Sprint 23)
* `search/QuickOpen.js`: Old export redirects ([`7d262804728`](https://github.com/adobe/brackets/commit/57d262804728b1d179f2e1a98e6932884c37e77b), Sprint _19_!) These were technically never deprecated, but they are also not documented either.

Few notes:
* Global CodeMirror object and old preferences conversion still present, awaiting official word if those should be removed or not. If so, I will update this to remove those.
* I came across this: [`672c7e`](https://github.com/adobe/brackets/commit/9672c7e19df84cc2bd84c807adc24fe870c0c042#diff-3) (`utils/StringMatch.js`), which landed in Sprint 25. I did not remove it for fear of breaking it because I do not know how that code works. Again, never deprecated, but it seems it was planned to be. @dangoor Since you made this commit, can you provide some insight here on what should be done?
* I have not checked extension compatibility yet, but all except the first item will be tricky to catch, as everything else was removing statements in the function/method, not directly access statements or APIs.