Added support for creating a new file. This extends the properties form to include the dimensions. This form appears when creating a new file, so you can specifiy dimensions, delimiter, and whether csv contains header row. The extension of the properties form also means that you can alter the number of rows/columns in the currently loaded CSV by going to File..Properties and changing the values. If you're reducing the number of rows or columns, then it'll prompt the user to confirm the data loss. Resolves #29. Resolves #3.