Replace DBSelectionExtension with annotations

[blafond]

fixes #1827

[DavideD]

Thanks, I gave it a quick look and left a couple of minor changes requests. I will try to review it properly tomorrow.

I think I prefer the Jupiter convention for annotations.
I would prefer something like this:

@EnabledFor(POSTGRES)
@DisabledFor(DB2)

[blafond]

@DavideD I re-worked the logic to implement ExecutionCondition like you suggested. It's lighter and cleaner and seems to work as expected.

The critical classes are: DisableForDBTypeCondition and EnableForDBTypeCondition

[DavideD]

Thanks @blafond, it looks much nicer now.

There are some minor changes to apply, but looks good overall.

The test related to the annotation at a method level could be grouped in a single class:

public class EnableForMethodTest  {

	@Test
	@EnableFor(value = POSTGRESQL)
	public void testEnable() {
		// Throw exception if this test is database is NOT POSTGRESQL
		assertEquals( POSTGRESQL, DatabaseConfiguration.dbType() );
	}

	@Test
	@EnableFor(value = POSTGRESQL)
	@EnableFor(value = MYSQL)
	public void testMultipleEnable() {
		// Throw exception if this test is run with POSTGRESQL or MYSQL database
		assertTrue( DatabaseConfiguration.dbType() == POSTGRESQL ||
							DatabaseConfiguration.dbType() == MYSQL );
	}

	@Test
	@EnableForGroup({
			@EnableFor(value = MYSQL),
			@EnableFor(value = POSTGRESQL)
	})
	public void testGroupEnable() {
		// Throw exception if this test is run with POSTGRESQL or MYSQL database
		assertTrue( DatabaseConfiguration.dbType() == POSTGRESQL ||
							DatabaseConfiguration.dbType() == MYSQL );
	}

       // Add the tests with disabled
}

This way we have less test classes around.
We probably could group togethere the others as well, but it would require to use subclasses and I'm not sure it's worth the effort.

[DavideD]

@blafond, could you also add the issue number in the title of the commits, please? It's quite helpful.

Use this format, please:

[#1827] Commit message 

Thanks

[blafond]

Implemented your changes/suggestions and checked formatting as well in my changed files. Found a few more unnecessary lines/comments.