Renew info about TLS in http api

[Zhaars]

Added info about setting default true value for the http_api_tls_transport_enable flag. Update tests to use HTTP API with tls.

Checklist

• [x] Change is covered by automated tests
• [ ] 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)
• [ ] CHANGELOG_DEV.md is updated
• [ ] Benchmark results are attached (if applicable)
• are up-to-date (in case of API changes)