SVGHMI: add static file serving feature.
Added two buttons to add and remove files.
Files are stored in project inside a directory named "static",
itself located in svghmi CTN instance files. Exemple :
exemples/svghmi_csv_json_img_table/svghmi_0@svghmi/static/
Files are transfered as "extra_files", but with a prefix
added to their name to avoid conflics.
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- Created with Inkscape (http://www.inkscape.org/) -->
<svg
xmlns:osb="http://www.openswatchbook.org/uri/2009/osb"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:cc="http://creativecommons.org/ns#"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:svg="http://www.w3.org/2000/svg"
xmlns="http://www.w3.org/2000/svg"
xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
inkscape:version="0.92.5 (2060ec1f9f, 2020-04-08)"
sodipodi:docname="default.svg"
id="hmi0"
version="1.1"
viewBox="0 0 1280 720"
height="720"
width="1280">
<rect
inkscape:label="HMI:Page:Home"
y="0"
x="0"
height="720"
width="1280"
id="rect1016"
style="color:#000000;opacity:1;fill:#d6d6d6;fill-opacity:1" />
</svg>
