Pier should verify the signature of blockheader of bitxhub

[Alexader]

Feature Request

Describe the feature you'd like:
Pier should verify the signature of blockheader from bitxhub before persisting.

Describe alternatives you've considered:
Lite module of Pier is responsible for synchronizing blockheader from bitxhub. But for now the blockheader is not verified.
The verification of signatures can be done with the help of out crypto module in bitxhub-kit project.