Reworked transaction creation function.

It now only translates the default message if necessary.
Fixed call to createTransaction() in session_login endpoint.
Typecheck the "default" message in createTransaction()
Abstracted the code to commit a transaction.

The code is now in db/connection.php
Added comment to finishTransaction()
Small change to initial build script.

Changed "dataType" in main data table to "datatype".
Bugfix for session_login endpoint.

Earlier detection of blank username and password fields.
Fixed log statements in cleanSessions()
Updated important documentation comment in api.php
Improved translation capabilities by adding strings to en_AU.json.

Added strings in db/connection.php
Actually added todo to working comments.

This probably shouldn't be a separate commit but oh well
Fixed bug with language detection.