Version 1.9.0 Release Candidate 4

Changelog:

• add compatibility with php8
• implement boot method for entities and traits
• wrap count query instead of modifying select clause
• implement filters (see https://tflori.github.io/orm/filters.html)
• implement morphed relations (see https://tflori.github.io/orm/relationDefinition.html#morphed-relation-1)