summarizeModel.loadLm: Extract model summary statistics from a loadLm model
In McDowellLab/loadflex: Models and Tools for Watershed Flux Estimates

Produce a 1-row data.frame of model metrics.

1 2	## S3 method for class 'loadLm' summarizeModel(load.model, ...)

`load.model`	A load model object, typically inheriting from loadModel and always implementing the loadModelInterface.
`...`	Other arguments passed to model-specific methods

Returns a 1-row data frame with the following columns:

site.id - the unique identifier of the site, as in metadata()
constituent - the unique identifier of the constituent, as in metadata()
eqn - the regression equation, possibly in the form const ~ model(x) where x is the Number of a pre-defined equation in rloadest::Models
RMSE - the square root of the mean squared error. Errors will be computed from either fluxes or concentrations, as determined by the value of pred.format that was passed to loadReg2() when this model was created
r.squared - the r-squared value, generalized for censored data, describing the amount of observed variation explained by the model
p.value - the p-value for the overall model fit
cor.resid - the serial correlation of the model residuals
PPCC - the probability plot correlation coefficient measuring the normality of the residuals
Intercept, lnQ, lnQ2, DECTIME, DECTIME2, sin.DECTIME, cos.DECTIME, etc. - the fitted value of the intercept and other terms included in this model (list differs by model equation)
Intercept.SE, lnQ.SE, lnQ2.SE, DECTIME.SE, DECTIME2.SE, sin.DECTIME.SE, cos.DECTIME.SE, etc. - the standard error of the fitted estimates of these terms
Intercept.p.value, lnQ.p.value, lnQ2.p.value, DECTIME.p.value, DECTIME2.p.value, sin.DECTIME.p.value, cos.DECTIME.p.value - the p-values for each of these model terms