fbmOptim

• Changed some code to match JSS paper.
• Commented on the line where Pearson kernels are always used for factor-type variables. Should this always be the case?
• Added control option to set intercept at a fixed value.
• Added (hidden) options for str() when printing ipriorKernel objects.
• Added fbmOptim() function to find optimum Hurst coefficient for fitting FBM I-prior models.
• Added new way to specify Hurst coefficient using the syntax kernel = "FBM,<value>".
• Wrote vignette manual guide which details how to calculate the matrices required for the closed form estimate of lambda.
• Removed the T2 statistic from the summary() output for now.