Use uniform format for <properties> and other tags

In settings.xml, the activationproperties have the format: <property><name/><value/></property>
whereas the 'user' properties below (which don't have any documentation) have the format
<my.property.name>my.property.value</my.property.name>.

They should really be uniform. My personal favourite is ofcourse: <property name="....">....</property>.

There are more places where duplicate classes are used (repositories,..).

(Also suggest to remove the <dependencies> tag from <dependencyManagement>
and make DependencyManagement extend from Dependencies (or, make it a list)., but this
could prove troublesome.)