elsa::complex is an alias for thrust::complex when quickvec is enabled,
and for std::complex otherwise

* Pass a default config to DataContainer.format, such that it can be
  passed in from the outside
* Move `format_config` into separate file to not create dependency cyles
* Add functionality to suppress or round small numbers to 0, such that
  instead of -1.49012e-08, only 0 is printed

In case of an error, print a version of the clang-format command
that will actually fix the error and not only print to standard out

Andi Braimllari authored Nov 11, 2021 and David Frank committed Nov 11, 2021

For further details check for example the numpy docs in:
https://numpy.org/doc/stable/reference/generated/numpy.fft.fftshift.html

The Makefile is just a convenience to more easily build elsa.

To build all of elsa, just call `make build` from the top level
directory. You can also pass any target to build, to specifically build
this target, e.g. `make build test_DataContainer`.

Other useful commands could `make tests`, to build and run all tests.
`make test <test-name>` to build a specific test case and run it.
And `make watch <test-name>` to build and run a test continuously on
code changes in elsa.

Note that a sub-folder structure will be created of the form
`build/$BUILD_TYPE/$COMPILER`. This enables quick iteration for
different build types and compilers, via passing the options
`BUILD_TYPE` and `CXX`.