API handle to get version of MapDB

[lhaeger]

Following up on #301 it seems even ten years later nobody has come up with "some trick" to read the MapDB version in running VM from code (or Google failed miserably in finding it).

Would you please reconsider implementing a simple getVersion() method?

[lhaeger]

Alternatively, please add the following two lines to the MANIFEST.MF in the package jar file:

Implementation-Title: MapDB
Implementation-Version: 3.0.9

so something like

	public static String getMapDBVersion()
	{
		return org.mapdb.DB.class.getPackage().getImplementationVersion();
	}

will do the trick.

Currently, this only returns null