Adding GARCH

[northern-64bit]

Description

Adding GARCH, its model fit and forecasts. It also reorganizes the econometrics menu.

How has this been tested?

Comparing to sample GARCH results from Hull.

Checklist:

• I have adhered to the GitFlow naming convention and my branch name is in the format of feature/feature-name or hotfix/hotfix-name.
• Update our documentation following these guidelines. Update any user guides that are affected by the changes.
• Update our tests following these guidelines.
• Make sure you are following our CONTRIBUTING guidelines.
• If a feature was added make sure to add it to the corresponding integration test script.

Others

• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.

[codecov]

Codecov Report

Patch coverage: 55.04% and project coverage change: -0.24 ⚠️

Comparison is base (df9a154) 58.29% compared to head (103b1a8) 58.05%.

❗ Current head 103b1a8 differs from pull request most recent head 3e52b2d. Consider uploading reports for the commit 3e52b2d to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4815      +/-   ##
===========================================
- Coverage    58.29%   58.05%   -0.24%     
===========================================
  Files          588      588              
  Lines        53666    53877     +211     
===========================================
- Hits         31283    31277       -6     
- Misses       22383    22600     +217     

Impacted Files	Coverage Δ
.../core/plots/plotly_ta/plugins/volatility_plugin.py	31.37% <0.00%> (-1.29%)	⬇️
...inal/core/sdk/controllers/crypto_sdk_controller.py	0.00% <ø> (ø)
...inal/core/sdk/controllers/stocks_sdk_controller.py	0.00% <ø> (ø)
...penbb_terminal/core/sdk/models/crypto_sdk_model.py	0.00% <0.00%> (ø)
...penbb_terminal/core/sdk/models/stocks_sdk_model.py	0.00% <0.00%> (ø)
openbb_terminal/core/sdk/sdk_helpers.py	36.92% <ø> (ø)
openbb_terminal/core/sdk/sdk_init.py	92.75% <ø> (ø)
openbb_terminal/core/sdk/trailmap.py	92.68% <ø> (ø)
openbb_terminal/dashboards/stream/Forecasting.py	0.00% <0.00%> (ø)
...bb_terminal/dashboards/stream/streamlit_helpers.py	0.00% <0.00%> (ø)
... and 41 more

... and 3 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[northern-64bit]

Note that running doctest on the example in the test fails:

I've now fixed it :)

[jmaslek]

Note that running doctest on the example in the test fails:

I've now fixed it :)

The docstring does not represent a functional example

    51         return np.asarray(x.iloc[:, 0])

ValueError: y must be squeezable to 1 dimension

You need to specify a column from the load. Also linters are failing