bumping LibCrypto verison to v2.1.0

Updated csproj files for pre-releases

- CompactCryptoGroupAlgebra v2.0.0-alpha2
- CompactCryptoGroupAlgebra.LibCrypto v1.0.0-alpha2

Renamed OpenSsl namespace to LibCrypto and added SPDX license informa…

…tion to comply with REUSE software specification.

Also added linking exception to GPL for CompactCryptoGroupAlgebra.LibCrypto.

Updated csproj files for pre-releases

- CompactCryptoGroupAlgebra v2.0.0-alpha2
- CompactCryptoGroupAlgebra.LibCrypto v1.0.0-alpha2

Nuget packaging + readme update