patched datetime PlominoField to use jquery widget
fixed template using JQUERY option
introduced jQuery datepicker, _temporarily_ in plomino.accordion.js
introduced plomino.datepicker.js
added starting_year and dateformat management between python and jQuery
DATETIME considered as single input field in case JQUERY widget choosen
Merge pull request #550 from gisweb/datetimeWidget

Introduced jQuery-ui datepicker widget for DATETIME fields