Resolves #34 "2500 limit" issue

Added application start-up event to check the data-type's prevalue column size.

If the prevalue column is set to be `nvarchar(2500)`, then the column is altered to be `ntext`.

The `ExpandPrevalueValueColumnSize` method is written by @mattbrailsford (credit goes to him).

Hopefully this code will resolve issue #34