Add type conversions for floating point numbers in sqlalchemy

[ehennenfent]

C:\Python3\lib\site-packages\sqlalchemy\sql\sqltypes.py:603: SAWarning: Dialect sqlite+pysqlite does *not* support Decimal objects natively, and SQLAlchemy must convert from floating point - rounding errors and other issues may occur. Please consider storing Decimal numbers as strings or integers on this platform for lossless storage.
  'storage.' % (dialect.name, dialect.driver))

SQLAlchemy complains about SQLite not having great handling for Decimal columns. We can add a TypeDecorator to fix this, but since it seems to be working right now, this is low priority.