Conseal

Added spatial embedding

- HILL

Added first spatial embeddings.

- HUGO
- LSB (replacement and matching, grayscale and color)

First release.

Implemented embeddings:

- J-UNIWARD
- UERD
- EBS
- nsF5

API on three abstraction levels:

- high-level (single call to embed)
- mid-level (moderate abstraction, separated cost from simulator)
- low-level (full access to cost computation, probability conversion, and simulator)

Fixed the source distribution.