New waveforms interface

Description

Incorporates the new waveforms interface.

Support calling C and python waveform models from C and python clients.

The standard functions XLALSimInspiralChooseFD(TD)Waveform and XLALSimInspiralChooseFD(TD)Modes remain backwards compatible.

New C functions have been added XLALSimInspiralGenerateFD(TD)Waveform(Modes) which replicate the old ones and support a more flexible input of the parameters. Equivalent functions exist for the python interface.

The LALSuite build system has been modified to support embedded python.

See here for a brief introduction on the new waveforms interface.

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

If any of the Backwards Incompatible check boxes are ticked please provide a justification why this change is necessary and why it needs to be done in a backwards incompatible way.

Review Status

Review chaired by @vijay.varma and @sascha.husa. Review wiki, review repo The review statement for the first stage of reviews is here.

lal/test/python/exclude-modules.txt

 # Add paths, relative to the `python/` directory to this file
 # to ignore them from the `test_python_imports.py` test script,
 # see /test/README.md in the upstream repo for more details
+
+lalsimulation.gwsignal
+lalsimulation.gwsignal.core
+lalsimulation.gwsignal.core.conditioning_subroutines
+lalsimulation.gwsignal.core.errors
+lalsimulation.gwsignal.core.gw
+lalsimulation.gwsignal.core.parameter_conventions
+lalsimulation.gwsignal.core.utils
+lalsimulation.gwsignal.core.waveform
+lalsimulation.gwsignal.core.waveform_conditioning
+lalsimulation.gwsignal.models
+lalsimulation.gwsignal.models.gwsurr