param_select: Optimise parameters
In mixchar: Mixture Model for the Deconvolution of Thermal Decay Curves

This function otimises parameter selection so that the model will ultimately converge.

1	param_select(theta, lb, ub, model, temp, obs, seed, restarts = 300)

`theta`	vector of starting values for each parameter
`lb`	vector of lower bounds on each parameter
`ub`	vector of upper bounds on each parameter
`model`	mathematical function to be applied
`temp`	temperature values
`obs`	DTG mass values
`seed`	random seed for optimiser
`restarts`	number of times for optimiser to restart