Refactor tests to use assertEquals

[dturner]

I've refactored TasksDaoTest to:

• use assertEquals because it's easier to read and removes the dependency on Hamcrest
• instantiate the database only once, then clear it before each test - should result in slightly faster test execution

Also did a very minor tidy up to AddEditTaskScreenTest to swap expected and actual values as they were the wrong way round.

[tunjid]

We probs still want to do this in @Before and @After so results of prior tests in the same test suite don't affect new ones

[dturner]

How would tests affect previous tests if we're calling clearAllTables @Before each test?