Changed keyboard to show on defined position.

* svghmi.js
added size paramter to edit_value
changed show_modal function to offset keyboard if paramter passed

*widget_input.ysl2
in on_edit_click:
function get position if key_pos element is defined in input widget

*widget_keypad.ysl2
Reworked keypad widget to extand class widget,
added support for changing keyboard position to user defined location

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# This file is part of Beremiz
# Copyright (C) 2019: Edouard TISSERANT
#
# See COPYING file for copyrights details.

from __future__ import absolute_import
from svghmi.svghmi import *