Allow searching for forms based on substrings

[czosel]

Currently, we're using the search param on the allForms query in the caluma form builder to search for forms, which doesn't do substring-matching (e.g. searching for "My" would not find "MyForm", but searching for "MyForm" would; the same goes for searching for questions). We could either adapt the search to do substring-based search or offer an additional param to allow switching between the two modes. We have to consider potential performance issues of substring-based search though.