* Merge initialize and initializeData in SolverInterfaceImpl.
* Merge initialize and initializeData in CouplingScheme.
* Update tests correspondingly
* Allow to check actions before initialize, especially checking whether initial data has to be written
* Check for sending and receiving of initial data during coupling scheme configuration
* Code simplification w.r.t waveform.
* Use dt=0.0 in actions in initialize.

Co-authored-by: Benjamin Uekermann <[email protected]>
Co-authored-by: Frédéric Simonis <[email protected]>

…recice#1352)

* Get tests and configs for serial implicit waveform interpolation from precice#1029.
* Differentiate between received initial data and data (from advance).
* Split data communication for SerialCouplingScheme and store initial data in waveform.
* Move common functionality of serial and parallel coupling scheme into BiCouplingScheme.

Co-authored-by: Benjamin Uekermann <[email protected]>

* Add test Integration/Serial/InitializeData/ImplicitBoth where both participants initialize.
* Allow initialize=true for both participants in serial-implicit coupling scheme.
* Raise warning, if first participant in serial coupling scheme initializes data with waveform order zero.
* Remove check for write data, because participant does not know about waveform order.

Co-authored-by: Benjamin Uekermann <[email protected]>

precice#1349)

…ng-in-initializedata