change comp_excln parameter to -1 (rank-ordered, deterministic sorting)

[ckoven]

This changes the default value of the comp_excln parameter to -1. This leads to the use of the rank-ordered sorting scheme, rather than the current-default probabilistic scheme. The main reason for doing this is that it results in fewer cohorts and therefore makes the model faster, which may be particularly important when increasing the number of canopy layers in #1315. It also has the effect of tending to slightly favor early-successional PFTs, as shown in fig. 13 of Koven et al, 2020, though that is not something that will show up in the kind of global nocomp and SP-mode simulations that this parameter file is currently mainly being aimed at.

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This will change answers in all cases other than SP.

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[rosiealice]

I think this is a good idea, as we noted, most of our implementations at the moment do not use the competition feature, leading to large duplication of cohorts betweem canopy layers, so this will likely provide non-trivial efficiencies....

[glemieux]

@ckoven should this close #303?

[ckoven]

@ckoven should this close #303?

That is so old I don't really remember the nature of the problem, but probably?