[form] fix #719285, due to multiple calls to restore_previous_post, by proper refactorings * move __init__ code from FieldsForm to Form. Must behaviour here should actually be in the Form base class * avoid buggy duplicated call to restore_previous_post * move some code that was in the form renderer to the form'__init__ method (__redirectpath & __form_id hidden input handling)) * 'formvid' should now be specified on form selection, not on form rendering

function load_now(eltsel, holesel, reloadable) {
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    var hole = lazydiv.children(holesel);
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    lazydiv.loadxhtml(lazydiv.attr('cubicweb:loadurl'));
}

function trigger_load(divid) {
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}