SVGHMI: Better and less verbose SVG namespace handling in XSLT transform

SVGHMI: Added mostly untested switch widget

SVGHMI: HMI:Page can now be a svg:g group or a svg:use clone, and included/linked widget are included in page. HMI:Jump was updated to be clickable through svg:use, to be generalized.

SVGHMI: ensure that coordinate in CSV file generated by inkscape are both matching svg default unit and in default reference frame

SVGHMI : still behave, even if important things are missing in SVG widget definitions (ex: needle missing for Meter widget)

SVGHMI : fix watchdog exception when timeout null

SVGHMI: be a bit more tolerant with missing HMI paths or missing elements in widgets : continue build (with warning) and fail silently at runtime.

SVGHMI : fixed bug happening when some SVG ids are containing dashes

SVGHMI : wait for initial timeout after watchdog is triggered, since it generaly induces HMI restart

SVGHMI : watchdog is now taking an initial and interval duration as CTN fields.

SVGHMI : avoid caching of xhtml file by forcing cache-control header in http response.

SVGHMI : HMI_STRING now also supported from HMI to PLC

SVGHMI : cosmetic

SVGHMI non significant fixes

SVGHMI : support for HMI_STRING and HMI_BOOL