The start of a memory recall ListView.

Summary:
- Add a `ListView` to `MainActivity` with the default `toString` of `MemoryEntry`

This doesn't actually let you recall memories yet, it just roughly shows them.

Test Plan:
- Ensured proper rendering with one memory.
- Ensured proper rendering with many memories.
- Ensured proper rendering with many **many** memories.
  - This test took place with 3107 rows in the memory_entries tables.
  - The app functioned fine, but startup took on the order of several seconds.
    - This is fixable by loading more as we scroll the `ListView`, but isn't a
      huge priority for the time being because it doesn't stop anything from
      working.

{F138}

{F139}

Reviewers: jcarter

Reviewed By: jcarter

Maniphest Tasks: T66

Differential Revision: https://phabricator.edgesysdesign.com/D69