Bug 22428: Change datatype of field_value to text

Bug 22428: Change datatype of field_value to text

This patch changes the datatype of the field_value column in
marc_modification_template_actions to "text". This is to stop text
strings longer than 100 characters from being chopped short and allow
longer strings up to 65,000 characters.

Test plan:
1) Follow the same steps outlined by Caroline in the problem statement
2) Apply patch
3) Follow the steps again and this time the text should upload with no
   problem

Signed-off-by: Caroline Cyr La Rose <caroline.cyr-la-rose@inlibro.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>