migrate: Clarify code and fix logic

!RESStorage.getItem('RES.firstRun.4.3.2.1') && -1 will either return
false or -1, never null, so the null case would never be run.
Switching to the use of 0 for the case allows us to consistently use
integers.
migrate: Simply with a conditional operator
migrate: Replace comment with variable
migrate: Refactor code into getOptionsVersion
fixes #1358 - found a nasty bug with image 'load' event -- height reports as same nubmer as width, which was screwing up the call to syncplaceholder!

there was also a goofy mixup of height/width elsewhere but oddly enough that didn't really affect/cause this bug...
Merge pull request #1381 from mc10/migrate

migrate: Clarify code and fix logic
bugfix to pageaction causing use subreddit style to act wonky on occasion
innerHTML -> textContent
subreddit mgr dropdown for a+b+c/foo/bar shows a/foo/bar, b/foo/bar, c/foo/bar

fixes #1361
Merge pull request #1361 from andytuba/issue_1361

Shortcuts dropdown menu: breaks when you have a shortcut that contains a forward slash
lots more innerHTML -> textContent cleanup where possible
innerText -> textContent