Initial commit of FlatOpcPackage and related classes
Fixed and enhanced packaging functionality, which now works with WordprocessingDocuments opened on FlatOpcPackages. Still totally undocumented.
Minor changes and refinements. Added comments. Still lacks validation of Flat OPC documents, basically relying on the Open XML SDK to write correct XML
Refactored Visual Studio Solution/Projects. Turned FlatOpcPackage tests into NUnit based tests.