Add ability to access current transaction info/transfers

[spencercorwin]

• Add transaction notifications
• Come back to ObjectBindingHelper.test.ts (testing notifications)
• Need to add transfers to script in UAPB.invokeRaw()
• Need to add coverage for this when added to blockchain.test.ts and transaction.test.ts
• Need notes in transaction.ts and index.d.ts
• Add to the tests file that are used in getSemanticDiagnostics.ts (valid.ts and complex.ts) then run tes
• Document notifications, stack items, stackitemtype, etc. in Index.d.ts
• Implement StackItems and Notifications in compiler
• Use ISTYPE opcode? Or create helper for IsBuiltinTypeHelper
• Notifications
• Need to add a types folder for notifications
• Need to add to all the builtin type stuff for notification
• Blockchain.currentTransaction.notifications
• Each notification has a script hash, eventname, and state = array of stack items
• Need to be able to parse the stack items
• Each stack item should be some sort of object with a type and then other key-value pairs depending on the type
• May need to add builtin type for StackItem and for each stackitem
• Then need to integrate APIs for those stack items into index.d.ts and the compiler
• Iterative over the state array and for each item determine its type and wrap that in an object with a type property which will be a number enum or a string (see how it was done with transactions)
• Test with Blockchain.test.ts in compiler
• Get notifications from Blockchain.currentTransaction?
• Or Blockchain.transfers?
• Blockchain.notifications
• Blockchain.currentNotifications