Accessibility - Filter form: fields without id + duplicate search id in the page

Accessibility issues on the filter form:

• duplicate "search" id in the page
• fields without id

<label for="reviewed" class="control-label">Minimum a reviews</label>
<select name="reviewed" class="form-control">(...)</select>

Pages affected by this bug:

• https://comptoir-du-libre.org/fr/users
• https://comptoir-du-libre.org/fr/softwares