Fix facet URLs for relative urls case (fixes #193)

Same as in commit 796059a388fa39573fb636469b6ca57eb28b2843: remove quirk
introduced in 2c087563c76d0430d8c83a52c79fdfc5adcea2a9 and add base_url
wrapper.
Merge branch 'develop' into feature-importexport
Remove useless </form>
Remove render_real_json in favor of fixing render_json