(TDD) Add skeleton of EntryLogAdapter as well as tests for it

*This pull request won't get merged in yet since it's not fully implemented.  It's just for making sure the skeleton of this class, as well as all of its tests, look good (this is for the TDD requirement in the testing requirements).*

Anyways, this pull request adds in the `EntryLogAdapter` class, which aims to make it easy to add `Entries` to the `EntryLogsActivity`'s list view. You use it by adding a number of budgets to it (which in turn will add their entries) and then binding it to the list view as you would normally an `ArrayAdapter`.

Then, you can use the various Comparators provided to sort the entries by different attributes.

Again, this isn't implemented yet; it's only tested.