Add support for parsing BitLocker metadata

Currently only support for metadata version 2 is implemented.

Tests are not part of the PR, I need to figure how to "minify" the BitLocker images.

Example of dump output:

$ sudo ./cryptsetup bitlkDump /dev/loop0
Info for BITLK device /dev/loop0.
Version:        2
GUID:           8f595209-f5b9-49a0-85d4-cb8f80258c27
Created:        Thu Jul  4 09:01:55 2019
Description:    DESKTOP-NPM7RCA H: 7/4/2019
Cipher name:    aes
Cipher mode:    xts-plain64
Cipher key:     128 bits

Keyslots:
 0: VMK
        GUID:           3e55195c-8811-4d9b-97b4-2b9e5f8f5384
        Protection:     VMK protected with passphrase
        Salt:           8d7637cc5d885d5ff4f748dbc8440d2e
        Key data size:  44 [bytes]
 1: VMK
        GUID:           64311dea-4587-4029-924a-ba299647998e
        Protection:     VMK protected with recovery passphrase
        Salt:           2ba080989af9b50c203aaebd0b40d498
        Key data size:  44 [bytes]
 2: FVEK
        Key data size:  44 [bytes]

Metadata segments:
 0: FVE metadata area
        Offset:         35213312 [bytes]
        Size:           65536 [bytes]
 1: FVE metadata area
        Offset:         46256128 [bytes]
        Size:           65536 [bytes]
 2: FVE metadata area
        Offset:         57909248 [bytes]
        Size:           65536 [bytes]
 3: Volume header
        Offset:         35278848 [bytes]
        Size:           8192 [bytes]
        Cipher:         aes-xts-plain64