Config file should allow disk encryption method to be variable

[bdemetris]

we force xts-aes 128 because thats what comes out of the box. we should allow for people to select anything they want.

[gavinelder]

Information about this command is here

https://docs.microsoft.com/en-us/powershell/module/bitlocker/enable-bitlocker?view=win10-ps

This is defined in create.go

Valid values are

Aes128, Aes256, XtsAes128, XtsAes256