Fixes the Open Line tests when the indentation is set as tabs in the main window

[TomMalbran]

I was running the test when I saw some fails in the Open Line tests. After some investigation I found out that it was because I had Tabs set as my indentation. So I fixed the tests so that they pass when Spaces or Tabs are set in the main editor.

[peterflynn]

I think it would be better to have the unit test force the specific preferences configuration it's expecting. With this change, the tests will test different things on different peoples' computers, which could be very confusing if only one version is failing.

Maybe in general tests that run in the Jasmine window should be isolated from the main Brackets prefs in the same way that tests popping up a separate window are...

[TomMalbran]

@peterflynn Makes sense. I updated the fix by setting the use of spaces and the space units when creating a mock editor, and used constants for all this stuff.

[redmunds]

This looks good.

The only question I have is about testing with the different indentation settings. It looks like all tests are now run with indentation set to 4 spaces. Seems like we should have some tests with Tabs and other lengths of spaces. Do we have them somewhere else and I am not seeing them? If not, are they appropriate here? If not, I'm OK with creating an issue so they get done at a later time.

Done with review.

[TomMalbran]

All the tests are only done with 4 spaces indentation (specially now that we set it for that instead of using the editor settings). Open line creates a new lines and uses the CodeMirror APIs to indent it. So not sure if it needs more tests with other indentations, but if it does you can open a new issue for that.

[redmunds]

Looks good. Merging.