segfault3 authored Oct 10, 2017 and Kai Lüke committed May 25, 2018

This is a combination of 4 commits:

- Disable "Encryption Options" for non-LUKS devices

- Disable "Change Passphrase" for non-LUKS devices

- Rename volume-content-luks to volume-content-crypto

- Add TCRYPT option widgets to the unlock dialog

This extends the unlock dialog by widgets which allow specifying the
parameters supported by TrueCrypt and VeraCrypt volumes. This includes:

 - Whether the volume to be unlocked is hidden.
 - Whether the volume to be unlocked is a system partition.
   Note: TrueCrypt and VeraCrypt only support encrypting Windows system
   partitions [1], so the label for this option is "Windows system".
 - Whether to use a PIM [2].
 - Whether to use one or multiple keyfiles. In the beginning there is
   only one button to choose a single keyfile. When a keyfile is chosen,
   another button appears below to allow selecting another keyfile, and
   so on.

Since TCRYPT volumes cannot be reliably detected as such, a label is
displayed at the top of the unlock dialog to indicate to the user that
this volume might not actually be encrypted.

[1] https://www.veracrypt.fr/en/System%20Encryption.html
[2] https://www.veracrypt.fr/en/Header%20Key%20Derivation.html