custom roles in package.xml

To use a custom installation role that another programmer has written, there are three steps that are necessary. First, the <usesrole> tag should be used to define each custom role that is used in the package.xml. Next, the role should simply be used for the files it pertains to. Finally, a dependency on the package that provides the custom role should be added to the package.xml, just for completeness.

Pretty simple!