v5.7.0-beta.1

Major updates

• Moving Jeebs.Cryptography over to use Option<T> fully
• Adding support for Option<T> JSON conversion
• Embedding version and adding new F.VersionF for retrieving Jeebs version
• Adding LazyAsync<T> type

Minor updates / fixes

• Removing double Catch() from F.OptionF.Filter / FilterAsync
• Removing some old references to IMsg?