applyTraitTradeOffs: Internal function to trade off one trait against another...
In HelenKettle/microPop: Modelling Microbial Populations

works by finding the values for each strain for par1 and par2 and then sorting them in opposite orders. This means the parameter values don't change number but they are assigned to different strains.

1 2	applyTraitTradeOffs(microbeNames, tradeOffParams, numPaths, numStrains, Pmats, resourceNames)

`microbeNames`	Vector of strings which contains the names of the microbial groups in the system e.g. c('Bacteroides','Acetogens')
`tradeOffParams`	(vector of two strings) - parameters to trade off against each other
`numPaths`	Named vector. Number of paths for each microbial group
`numStrains`	Scalar. Number of strains per group
`Pmats`	List containing lists and matrices: [[param]][[strainName]][path,rname]
`resourceNames`	Vector of strings which contains the names of the resources in the system