Add configuration for an alternate pastebin upload helper command

[mtmiller]

It seems that the interface for "upload to a pastebin service" simply requires any program that takes text on stdin and reports a URL on stdout. This is great, and very simple, which means that the user could use an alternative to wgetpaste for the same functionality. Would you consider adding a configuration key for the name of the upload helper command?

As an example, on my Debian system, I don't have wgetpaste, but I do have pastebinit. I added a simple wrapper shim called wgetpaste to run exec pastebinit on my PATH, and now gpaste-client upload works perfectly. It would be so much simpler if I could configure that with gsettings and not need a shim script.

[jeffr1975]

I would use this feature. Working on a shim right now.