Clean Up Unit Tests Part 1

Part of #256, #257

A few things going on here:

 * Re-enable the following tests by getting them to read test resources properly:
   * AzkabanDatabaseUpdaterTest
     * testH2AutoCreate
   * JavaProcessJobTest (all tests)
   * JobTypeManagerTest (all tests)
   * ProcessJobTest (all tests)
   * FileIOUtilsTest (all tests)
   * Total for azkaban-common: **58 tests passing, 26 tests skipped** (vs before: 47 tests passing, 37 tests skipped)
 * Use JUnit's TemporaryFolder to provide temporary directories and temporary files for tests so they stop polluting the source tree with their output
 * Have Gradle package up the test projects in azkaban-test