Add a boundary layer module to estimate boundary height

[ThomasRieutord]

Add a boundary layer module to estimate boundary height with various classical ways from vertical profiles

Description Of Changes

Boundary layer height estimation is a parameter commonly derived from vertical profiles (from radiosondings or model profiles) with key importance in application domains such as air quality. The issue #1515 was expressing the need for a way to estimate boundary layer height with MetPy. This PR suggests a module in calc to do so.

The newly added module boundarylayer.py includes four different ways to estimate the boundary layer height, each of them is linked to references:

• from bulk Richardson number
• from the parcel method
• from humidity gradient
• from temperature inversion

Help needed

The imports in the module do not follow the MetPy standards. They are just as if MetPy was an external module. Can someone help me correcting them?

The decorators that are present on the functions of other modules (such as exporter) are missing. As I'm not familiar with them, help is welcome here too.

The testing program added together with the module only runs the functions in the new module on sample data, but the unitary tests are not defined yet.

Thanks for your help.

Checklist

• [x] Closes #1515
• [x] Tests added: not to the Pytest format yet
• [x] Fully documented