0.8.0 release

This is interim release with some important breaking changes and improvements:

• BREAKING CHANGE: SYSTEM-EXISTS-P was renamed to SYSTEM-REF.
• Tests fixed to work with the latest version of Parachute test framework.
• Added test coverage measuring.
• Removed boxing warning when using function types as component slots.
• It is now possible to re-initialize global entity defined with DEFENTITY by funcalling its ctor from INIT-GLOBAL-ENTITY symbol property.

See changelog for a full list of changes.