Support VeraCrypt

Submitted by segfault3 @segfault3

Link to original bug (#796146)

Description

This is part of the ongoing effort to integrate TrueCrypt/VeraCrypt support into GNOME. The attached patch extends the unlock dialog to support parameters required to unlock TrueCrypt/VeraCrypt volumes. It requires udisks patches which were merged (see https://github.com/storaged-project/udisks/pull/495), but not released yet.

See also the thread on the devkit-devel mailing list: https://lists.freedesktop.org/archives/devkit-devel/2017-November/001800.html