Code Changes and Clean up

1: Removed port specification from the IPN callback url. Improves
reliability over SSL/non-SSL connections
2: Moved some string constants to *consts* php file
3: Wording changes for some messages
4: Retrieve and save transaction id to database
5: Use ‘item_number’ index of IPN array to retrieve VPGH reservation
key value
6: Use ‘item_number’ index of IPN array to retrieve Paypal transaction
id
7: Added database changes to .install file to rename some indexes and
add trans id column to reservations table