Note list: Alphabetical sorting should discard "hidden" Markdown characters

If you have Markdown notes that start with a header, e.g. `# 3`, it will sort to the top of the notes list due to the initial character, even though we strip that out for display.

This is also an issue in iOS at least, maybe everywhere: https://github.com/Automattic/simplenote-ios/issues/340

Start by tracing the note-list alphabetical sorting and the Markdown display-stripping behavior, then reproduce the issue with a note beginning `# 3`. Done means notes sort according to their displayed text rather than hidden Markdown characters; the issue provides no file or test names, so locate the relevant entry point and tests first.

Written by the indexing model from the issue text.