Updated Paypal accepted currencies

According to https://developer.paypal.com/webapps/developer/docs/classic/api/currency_codes/#paypal
Replaces PR #815 Shipping files fixes

Replaces PR #815, which fixes #683, #793, #803, #865, #870. There were
too many changes to deal with, so I decided it was faster to start from
scratch.
Check for visitor database ready before executing transaction
Merge pull request #887 from JeffPyeBrook/pr-visitor-meta

Check for visitor database ready before executing transaction
WHen new visitor can't be created use the bot user id and emulate setting the cookie
Merge pull request #888 from JeffPyeBrook/pr-visitor-meta

When new visitor can't be created use the bot user id and emulate settin...
return empty cart when cart cannot be retreived from database
return cart passed as parameter when cart cannot be sotred into database
Merge pull request #889 from JeffPyeBrook/pr-visitor-meta

Return empty cart when cart cannot be retrieved from database
Check for tables existing even if database version is correct in case upgrade failed.
This would allow the best chance of recovery in the wordpress admin screens
Use show tables query instead of information schema
Changed show tables query
Modify visitor API database check.
added missing return value
adjsuted initialization logic to handle bot user id's, invalid user id from wp
added blank line
Merge commit '555d1b32b616bdf38ed8f98d182e54d991e27d06' into pr-visitor-meta

Conflicts:
	wpsc-includes/wpsc-meta-visitor.php
Merge pull request #890 from JeffPyeBrook/pr-visitor-meta

Check for tables existing even if database version is correct
Clear customer meta on clear auth cookie.
Clear customer meta on clear auth cookie, properly
Unset customer cookie properly.
Merge pull request #867 from misulicus/patch-10

Updated Paypal accepted currencies