Cleaning up my mess

[belcar-s]

I've been bothered lately by some problems in the parts that I’ve written. Most importantly, these changes replace somewhat exceptional code with code that fits in better with the rest of the project; I'm hoping that I made the activate function easier to understand.

• A useless if statement was also removed,
• I restored reporting of some errors produced in client_disposable.ts —errors which must be very infrequent, since most of the file lies inside a try/catch,
• and a simpler, less awful method is now used to remove an item from an array in the registerEditorWatcher function.

[belcar-s]

Sorry to bombard you with so many pull requests. I realize you're on holiday, so please don't feel pressured to review these right away 🙂.

[sgwilym]

Thank you for being so patient with me reviewing these contributions.