Add missing include for use of std::runtime_error and fix C++17 uses

See merge request !74

Fix oskar build

See merge request !73

Remove redundant copy of skalowmini-coef.tm

See merge request !71

Fix building without tests

Closes #54

See merge request !70

Fix finding FFTW3 libraries

Closes #53

See merge request !69

The build was broken when CMake configuring using -DBUILD_TESTING=OFF.
This has been fixed.

Fixes #54

FindFFTW3.cmake should also use FFTW_ROOT_DIR environment variable when
searching for the FFTW libraries.

Fixes #53

Merge branch '52-dp3-tapplybeam-test-fails-due-to-bug-in-station-computeelementresponse' into 'master'

Resolve "DP3 tApplyBeam test fails due to bug in Station::ComputeElementResponse"

Closes #52

See merge request !68

Remove some duplicate code

See merge request !67

Resolve "generalize lofar and oskar telescopes"

Closes #51

See merge request !65

Oskar unit test

See merge request !66

Resolve "Speed up MWA primarybeam calculation"

Closes #50

See merge request !64

Resolve "Add support for using of the OSKAR beam model in wsclean"

Closes #49

See merge request !62

Minor fix in everybeam primarybeam calculation

See merge request !63

Resolve "Integrate primary beam functionality I - III"

Closes #45

See merge request !51

Resolve "Revert CI/CD scripts to use main OSKAR repository again"

Closes #48

See merge request !61

Resolve "Add stationresponse comparison for oskar"

Closes #46

See merge request !59

This is needed in cases where the ElementResponse needs
additional arguments in the construction.