px:fileset-load @method option. Tests for filesets and mediatype.

px:fileset-load: the @method="xml|html|text|binary" option lets you override the default load behavior. For instance, if you know that "bin.dat" is an XML-file, you can set @method="xml" to load it as XML.

Added a bunch of XProc tests for px:fileset-load, px:fileset-filter and px:mediatype-detect.
merge validation-utils
Added d:error-count to the XProc validation reports.
merge validation utils attempt #2

Conflicts:
	validation-utils/src/main/resources/xml/xproc/validation-report-to-html.xpl
Merge pull request #4 from daisy-consortium/fileset-load-method-and-tests

Fileset load method and tests