Adopt formatOnSave changes

[jrieken]

Since we now have the editor.formatOnSave-setting and the onWillSaveTextDocument event, this code should be updated. Using the new infrastructure will prevent unnecessary fs-operations, event cascades, and potential for endless write-event-write loops.

See https://code.visualstudio.com/updates#_format-on-save, microsoft/vscode#12449, and microsoft/vscode#239 for more details

[HookyQR]

Thanks for the nudge @jrieken. I'm on it. 🛠

[HookyQR]

@jrieken: Something that I have found to be lacking in the docs, at what version does this kick in? I'm guessing it's at 1.6.0, but it would be nice if an 'as of' was mentioned in the api docs.

[jrieken]

Understood - what we do is to fetch the version of vscode.d.ts according to the engine-property in your package.json file.

[HookyQR]

@jrieken, I mean, at https://code.visualstudio.com/docs/extensionAPI/vscode-api it would be nice if each of the methods had a reference to the version in which they became/become available.

[HookyQR]

Done in v0.5.0