Enable tests to be run without running any UI tests

This branch moves the UI/activity related tests to their own package.

Then, I added an `ant` target called `skip-ui-tests`. If this target is specified before the `unittests` target (for example, as `ant clean skip-ui-tests emma unittests`), it will execute all tests except for things in the `com.example.budgetmanager.ui.test`.

This should make our tests 'pass' on Jenkins more often (and thus our build will succeed more), but it will lower the reported code coverage due to a bunch of tests not being run. Thus, when testing for code coverage, we have to run the tests on our own machines without the `skip-ui-tests` target specified.

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Also fixes some `checkstyle` problems.