display modal form in the bootstrap4 theme

add Enum type for python < 3.4 by using backported enum34 package

Update jquery, moment dependencies and references in templates

Letting the edit html inherit from right source in form-files-field example

update to latest mapboxUrl API to get the styled tiles in leaflet

Fixed date field just allows to pick date <= 2015

Support search on SQLAlchemy hybrid property

Update requirements.txt

Sqlalchemy utils types

fix The mongoengine example does not work #1865

Use consistent case for func.ST_AsGeoJSON

Simplify example code