Upgrade Ace Editor

(NOTE: Not yet ready but placing this here for later review)

This PR updates our internal version of Ace to its current release, [1.1.8](https://github.com/ajaxorg/ace/releases/tag/v1.1.8).

Thus far, there have been a number of necessary changes to our tokenization rules:

1. The tokenizer no longer includes the 'column' a token is found at, in its `getLineTokens()` call, so we have to patch that back in (we rely on it heavily to translate between document-coordinates and token-coordinates)

2. The regex matching rules now merge tokens within a rule by default, and this implies that e.g. `[[(` would be merged into a single `lparen` token. We can opt out by specifying `merge = FALSE`.