Use class constants instead of constructor arguments
New entry in $call_list(VerifyAddItem) and new Description method

Description on eBay needs to be CDATA if it contains HTML, which it
will.
This is, so far, the only mothod which cannot be covered by __call()
Apply from stash to restore Description method & VerifyAddItem in $call_list
Merge branch 'dev' of github.com:Kern-River-Corp/eBay-API

Conflicts:
	ebay_api_call.php