Execute callbacks after transaction is closed

In latest Chrome, the request's onSuccess handler sometimes is fired
bfore the transaction is closed. If the handler function then calls a
method that opens another transaction, the IDB implementation will
operate the second transaction on the state of the database as it was
prior to the first transaction.

Refs #26
tr callback for get()
tr callback for batch
Add tr callbacks to getAll
Extract native getAll
Refactoring
Fix wrong comma
Add tr callbacks for clear
Add tr callbacks to iterate
Add tr callbacks for count
Remove unused param
Remove duplication
Update changelog
Make new build
Merge branch 'trcallbacks' into develop