All apps should ignore build and deploy store

[preaction]

Application's source stores should ignore everything in any destination store. If we have a build store that happens to be under a source store, like:

• / <- the source root
• /_build <- the build destination

If we have certain apps using / as a source (like the plain app), they might find documents in the /_build directory (especially if the static app moved them there).

No matter what, all of the possible destination directories are not to be searched for documents.

[preaction]

This is especially a problem for the static app, because it will start creating new copies of the build directory over and over and over until it reaches an insane level of depth...

[preaction]

This is especially a problem when deploying, because it will cause major errors if you're (properly) ignoring the build directory in .gitignore.

[preaction]

In essence, all file-based Stores should ignore each other's directories. Move Statocles::Store to Statocles::Store::File (include a base role for latching on to) and keep track of all the directories being watched by stores to ensure that find_files() and read_documents() do not take things from other stores.

This seems like the most elegant way of doing it, for now...