MySQL encoding data types

[Zhaars]

Basic implementation and code refactoring regarding data type encoding in MySQL based on @Lagovas PR for PostgreSQL.

Checklist

• [x] Change is covered by automated tests
• [x] The coding guidelines are followed
• [x] Public API has proper documentation in the Acra documentation site or has PR on documentation repository with new changes
• [x] CHANGELOG.md is updated (in case of notable or breaking changes)
• [x] CHANGELOG_DEV.md is updated
• [x] Benchmark results are attached (if applicable)
• x are up-to-date (in case of API changes)

[Lagovas]

in general looks great except question about returning error in binary encoding. improvements related to type conversions are questionable)