- Fix bad metadata
 - Change unpractical tag names (used to be fully qualified java class)
Added optional return types for adapter methods:

		<methods>
			<method name="value" type="any" valueField="columnValue">
				<param name="name" field="columnName" type="string" required="true"
/>
			</method>
		</methods>
Reduce interface usage.
The link between mailmap and attachment is the only one using an
interface, and it complicates API code. It's fixable, but for one class
(presumably to be able to use the DummyAttachment map) it isn't worth it
Added sort of dummy constructor, as adapters are supposed to have a
default constructor.
Fix missing getters. Requiring getters is cleaner, it makes it a lot
easier to generate API code. (Most importantly, it allows API code to be
generated without the actual adapter code). Making getters is a bit of a
chore, but worth it in the end