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
Merge pull request #815 from ReactorShop/master

PR for issues #803, #683 (Shipping files fix)
Add 'wpsc_gateway_name' filter.
Remove Google Checkout from wpsc_gateway_name filter.
Inline documentation for wpsc_gateway_name().
Update logic that checks if a visit is a web bot
* Change preg_match to str search for performance and readability as recomended by note in http://us1.php.net/preg_match
* Check if user agent string is defined and not empty prior to to text comparisons against it
* Hook to allow override of bot detection will always be available instead of only when wpec decides visit is not a bot
Visitor profile expiration time advancement
* advance the profile expiration time whenever the last active time is being set to the current time
* timestamps can be passed as timestamp strings or as unix times
Merge pull request #891 from benhuson/_wpsc_gateway_name_filter_2

Add 'wpsc_gateway_name' filter (rebased)