Document cloneProduct method

First pass at documenting the cloneProduct method
Document createProduct method
Document deleteProduct method

and general cleanup of method doc
Merge branch 'master' into devdocs
Add product and variant method docs
Merge pull request #18 from ongoworks/devdocs

Create basic developer docs for product methods
Merge branch 'v0.1.6' into inventorytracking
Remove field validation if disabled