Currently it was only possible to use "Exit with External Tool.."
menu option in Writer. Now it is also possible to use this in
Calc and in future Draw and Impress. Code has been refactored and
extacted out of "sw" into "svx", so other components can use it.
Currently there is no cleanup of temporary images after processing
was done, and also pinging for changes are still active even when
editing in external tool is done. This behavior will be changed
in the future.
Change-Id: I09969d44dfddbf9183b30ff3fffa2d201c7ae40f
