speedy: fix prompt handling for sysops
speedy: avoid deadlocks when deleting a page alongside its talk page

Per issue #147.
Also includes a fix to the status output of automatic redirect deletion.
speedy: don't automatically open talk page when prompting for deletion summary

To prevent confusion and focus the user on the modal prompt.

Add space to deletion summary
warn: add custom warning feature

You can set up custom warning templates using TWPREFS and then apply
them the usual way. Quite simple, really.
morebits: fix minor bug in splitWeightedByKeys

When the start delimiter occurs at position 0, the function would always return an empty array, regardless of how many other times the delimiter occurs.
unlink: require input in the reason field

Common sense.
morebits, protect: move edit/move protection preservation logic into morebits

This logic preserves existing move protection settings when edit protection is applied by itself, and vice versa.
It is also needed in batchprotect, and it should also be useful functionality for end-users, so it now lives in Morebits.wiki.page for all to use.
morebits, protect, batchdelete: a few bonus fixes

- protect's "custom expiry time" prompt: if you cancelled the prompt and then submitted the form, an invalid value would be submitted to the API.
- Morebits.wikitext: no double space before commented-out images.
- batchdelete: now shows a status message when you first open it, just like unlink and batchprotect
tag: always start merge discussions on the destination page

Per request at WT:TW.
morebits: more robust failure handling in wiki.api and wiki.page

To answer the comment on line 2570/2606, which I am removing, we certainly do need the failure callbacks.
They are crucial for tracking the completion of individual tasks in a batch operation.
Without failure callbacks, a failing task looks the same as one that hasn't completed yet, meaning the batch operation can hang if there are too many individual failures.

As for wiki.api's error handling, I think it's fine; UncleDouggie wrote that comment back in e8cc3724577fafe97c9c4a5ec6b5ce48e5c48f70, and only he knows what he had in mind for wiki.api.

Also fixing a long-standing bug - "invalid title" errors were never caught properly.
config: tweak to helptip for custom warning pref

Hopefully, making it a bit clearer.
config: make helptip links open in a new window

So pref choices aren't lost when these links are clicked.
tag: convert tag-specific prompt dialogs into subgroups;

- Most prompts for article tags are now implemented as subgroups, to
provide a smoother experience for the user.
Allow chaining of methods for Morebits.simpleWindow