Fixes #4905: Error while trying to set "weight" in Variant with "," as seperator.

Fixes #4905
Fixes #4939
Refactor number parsing to be DRY. Fixes #4939

Conflicts:
	core/lib/spree/core.rb
	core/spec/models/spree/variant_spec.rb
	core/spec/spec_helper.rb
Fixes product validation on create. Fixes #5588

Conflicts:
	api/app/controllers/spree/api/base_controller.rb
	core/app/models/spree/product.rb
	core/app/models/spree/variant.rb
Fix git conflict.
Remove file that shouldnt exist.
Give spec correct title.

fixes #5614