Ensure property containers use unique IDs with multiple fieldsets

...by adding the current Archetype's Umbraco Property Alias to the ID string

Old: archetype-property-0-0
New: archetype-property-sliderItems-0-0

Need to DRY this up later ;)
Merge pull request #52 from imulus/fix-ids

Fix some datatypes not working with multiple Archetypes
Merge pull request #54 from imulus/develop

Develop