Addition of WaveX model

[LuluAgazie]

1. Implementing the Wave model (models/wavex.py) as a timing model DelayComponent with parameters:

• WXEPOCH (MJDParameter): reference epoch either set by user or copied from PEPOCH - frozen
• WXFREQ_000X (prefixParameter) [days^-1]: Wave frequencies set by user with integer label X - frozen
• WXSIN_000X (prefixParameter) [s]: Sine amplitude corresponding to frequency X - free parameter
• WXCOS_000X (prefixParameter) [s]: Cosine amplitude corresponding to frequency X - free parameter

2. WaveX model can be read from par file or user can add it as a timing model component
3. Added test script tests/test_wavex.py

Examples:

1. Making fake noiseless TOAs with a model containing no WaveX component and looking at prefit residuals with models containing 1-3 WaveX components show expected sinusoidal behavior

One component: WXFREQ_0001 = 0.01 days^-1
Two component: WXFREQ_0001 = 0.01 days^-1 ; WXFREQ_0002 = 0.1 days^-1
Three component: WXFREQ_0001 = 0.01 days^-1 ; WXFREQ_0002 = 0.2 days^-1 ; WXFREQ_0003 = 0.5 days^-1

2. Making fake noiseless TOAs with a model containing one WaveX component and fitting for sine and cosine amplitude:

Prefit model WaveX component :
WaveX(
MJDParameter( WXEPOCH 55321.0000000000000000 (d) frozen=True),
floatParameter( WXFREQ_0001 0.1 (1 / d) frozen=True),
floatParameter( WXSIN_0001 0.001 (s) +/- 0.0 s frozen=False),
floatParameter( WXCOS_0001 0.0 (s) +/- 0.0 s frozen=False))

Postfit model results for WaveX component:
WaveX(
MJDParameter( WXEPOCH 55321.0000000000000000 (d) frozen=True),
floatParameter( WXFREQ_0001 0.1 (1 / d) frozen=True),
floatParameter( WXSIN_0001 0.001000038898416328 (s) +/- 4.481880899175662e-08 s frozen=False),
floatParameter( WXCOS_0001 -3.283614132428176e-08 (s) +/- 4.4763897206286186e-08 s frozen=False))

TO DO: conversion from Wave to WaveX

[codecov]

Codecov Report

Patch coverage: 67.86% and no project coverage change.

Comparison is base (3a2910f) 68.25% compared to head (325940e) 68.26%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #1609    +/-   ##
========================================
  Coverage   68.25%   68.26%            
========================================
  Files          99      100     +1     
  Lines       22806    23108   +302     
  Branches     3920     4009    +89     
========================================
+ Hits        15567    15774   +207     
- Misses       6276     6343    +67     
- Partials      963      991    +28     

Files Changed	Coverage Δ
src/pint/models/timing_model.py	83.62% <ø> (ø)
src/pint/utils.py	57.81% <44.53%> (-2.30%)	⬇️
src/pint/models/wave.py	80.30% <58.82%> (-2.39%)	⬇️
src/pint/models/wavex.py	87.42% <87.42%> (ø)
src/pint/models/__init__.py	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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[abhisrkckl]

I have merged David's RTD fix PR. Can you merge the master here?

[abhisrkckl]

If you are using logging, it's better to use loguru since that's what the rest of pint uses.

[abhisrkckl]

Hi.. I see that the patch coverage is only 63%. Can you make sure that it's at least 70%?