Split shortcuts by platform and name them

[hpohlmeyer]

The main task of this pull request is to name the default shortcuts.

I think the default shortcuts are not bad, but if you want to use mobiledoc kit as a framework you need a way to reset the shortcuts and not just overwrite them. (For example, if you do not want to support underlined text)

You already have the unregisterKeyCommands() function to delete key commands. Unfortunately, the shortcuts need a name property to delete them. This is what I did for the default commands.

Some of them had different functions, depending on the platform. This is why I split the arrays into a mac and a windows array. This way I could give them distinctive names.

[hpohlmeyer]

Another approach to this would be to change the unregisterKeyCommands() function to take the key command instead of a name. This way you do not even remember the name of the shortcut, but can delete the unwanted shortcut.

[hpohlmeyer]

Travis CI fails, because some of the key commands don’t work anymore. For example CTRL+B worked on macs, but did the same as CMD+B. All windows commands, that use CTRL as a modifier are now associated with CMD on mac.

Before I start modifing the test, I would like to know if you welcome these changes. Thanks!

[mixonic]

@hpohlmeyer thanks for diving in here, I've made a note to try and follow up on Friday. 🙇

[lukemelia]

I ran into a similar issue as @hpohlmeyer and am supportive of his proposed change.

[hpohlmeyer]

Closing this as @lukemelia has a modernized version of this PR in #789.