Override mopa template

This file is an exact copy of the corresponding MopaBootstrap file, but
for 2 lines (identified with {# ZBOUBIDOO #} tags). This solves
form-error-messages display issues (for date type and file-input type).
Note that those problems are solved in the current release of Bootstrap
(which we cannot use yet because leafo isn’t working with the very last
release of bootstrap less).