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.
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
Removed timezone handling in the process (needs to be documented).
Note: on_conflict does not check for constraints (needs to be documented).
Note: some of the constraints tests seem to be aiming for a different static_assert.
