dependency field not defined as ComplexType

[mbjones]

The current eml-software dependency element is defined as a global element in eml-software, and then used in the schema in other locations by referencing the global like so:

<xs:element ref="dependency" minOccurs="0" maxOccurs="unbounded">

We got rid of this style in favor of using named ComplexTypes, and this one should be no different. Rearrange the schema to make this a DependencyType Complext Type, and get rid of the ref references.

[mbjones]

Completed switch to ComplexType, and added software example for testing.