Issues fixed

#2: support several rdb access interfaces

• now supports PDO directly, so DBAL is no longer a requirement

#3: PSR-2

#4: blocked counters need unit tests

#5: api docs for statistics functions

Supports fixed execution times

• Added functions for fixed execution times to mitigate timing attacks
  with parameters and docs
• Test of DbalGateway added
• doc/Installation.md added keepCountsFor parameter to configurations

Usable but not up to standards

• Factored out from metaclass-nl/authentication-guard-bundle
• with api to support custom extensions for NoSQL storage
• User agent no longer tracked
• Improved documentation with databse indexes and defs