Signatures - signing subkey selection

[Achim16]

You might want to consider that keys can have several subkeys eligible for signing
so that a key selection could show subkeys, see image of how WinPT for GPG legacy handles this.

[saturneric]

After some research on my part, the programming interface provided by GnuPG (GPGME) does not currently support specifying a specific subkey in an operation. However, GnuPG itself supports it with its command options. Things get a little more complicated, and I don't really want to go directly to GPG and operate through the interface they provide.

So, this requirement may be placed for a while longer. I may find time to provide them with feedback and expect them to provide such support.