Adding prognostic chlorophyll to WOMBATlite generic tracers (#10)

* Added "pchl" as a new tracer to WOMBATlite. Working fine. Currently mirrors the "phy" tracer.

* New light attenuation scheme working. Considers blue, green and red light and their different attenuation given chlorophyll concentration.

* Chlorophyll appears to be working well. Some outstanding issues but model is stable. Also converted all units of biomasses to carbon, rather than nitrogen. Altered some parameter coefficients as well, such as abio and alphabio.

* Made 4 very slight changes to the code to account for Dougie Squire's review. All regarding syntax. No changes to equations.

* Fixed a bug in the iron cycle, where I was previously making iron too limiting to phytoplankton. This will change a lot in the next branch focussed on iron cycle development though. I also took the opportunity to change the names of the parameters for WOMBAT-lite and their default values.

* Made slight changes to (1) where we now calculate the mean light in the grid cell, not the mid point; (2) we save both the mid point and mean to diagnostic output (radmid and radbio); (3) renamed phy_lday to phy_leup because it makes more sense; (4) removed unecessary code snippets; (5) syntax changes for consistency

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Co-authored-by: Pearse Buchanan <[email protected]>
Co-authored-by: Pearse Buchanan <[email protected]>
Co-authored-by: Pearse Buchanan <[email protected]>
Co-authored-by: Pearse Buchanan <[email protected]>
Co-authored-by: Pearse Buchanan <[email protected]>

Author: 6 people