The library is header only. It makes no sense to distinuish
between the standard the library is compiled with and the
standard the tests are compiled with. The library does not
get compiled on its own.
* Replace connection handle method check_connection() with is_connected() and ping_server()
* When a connections is fetched from a pool perform a validity check which can be one of none, passive or ping.
* Add the methods is_connected() and ping_server() to the connection template class.
* Remove unused #include and add mising #include.
* Add tests for the connection methods is_connected() and ping_server().
Add support for connection pooling
* Add support for connection pooling to the core code.
* Add support for PostgreSQL connection pooling with tests.
* Add support for SQLite3 connection pooling with tests.
* Add support for MySQL connection pooling with tests.
Add Connector Cmake logic
* Also install date when used with fetch content
* Install everything always
* Update documentation
* Add option to control dependency searching
* Adjust travis
