v0.6.0

• New Program type, separated from a virtual machine VM.
• Program may restrict total number of libraries via const generic parameter.
• Prohibit programs with no libraries or code ("empty")
• Convenience constructor for programs containing multiple libraries.
• Add support for optional strict encoding of a program data
• Add optional serde encoding of a program data

Full Changelog: v0.5.0...v0.6.0