MVP Position List implementation

[chocolatkey]

• Add missing presentation properties to manifest
• Add new convenience function to publication for finding a resource in the manifest based on a (cleaned) path
• Add position list service
  • Needed to implement services concept
  • Locator-related structs and tests
  • EPUB position service, Per resource position service (for e.g. cbz)
  • No Audio position service - should it be included in an MVP? (not very difficult to implement)