PTDB first update

Updates

Fixes a bug that causes a FileNotFound error when trying to save or modify a database with no filename
Fixes a bug that stopped empty attributes defined as '[]' to be checked properly.
This is some what a 'new' feature, but I will leave it as a bug because it was mean't to do this from the beginning and I forgot to readd it; Fixed a bug in the parsing that didn't let the column type define the value type in the Ptdb Object.
Fixes a bug that would cause an error when checking for an item in a column different than 'STRING'
Other small bugs fixed.
Extra: Added better source code documentation.