Increase the length of the PurposeOfLoan field

[grantfitzsimmons]

We should increase the PurposeOfLoan field in the loantable to at least 128 characters.

From Jordi at MCNB on Trello:

The field purposeOfLoan in the Loan table has 64 chararter leght, is it possible to expand the field al least 128 chararters?

We usually put the name of the exhibition in this field when it is a cultural loan, and with 64 characters it is a bit limited. Otherwise, we will use the remarks field.