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

#
# Dockerfile for wxPython3.0 running on python2.7
#

FROM python:2.7-stretch

RUN set -xe \
    && apt-get update \
    && apt-get install -y --no-install-recommends python-wxgtk3.0 python-matplotlib \
    && apt-get install -y --no-install-recommends python-xvfbwrapper xvfb \
    && apt-get clean