rqtl/qtl2: Version 0.22-8

Numerous small changes to get the package on CRAN. Added R Core Team as a contributor, as the package includes a copy of code for Brent's method for univariate function optimization, taken from R version 3.2.2. Also added a Copyright field in the DESCRIPTION file. Sped up some of the examples and tests. Tests no longer use more than 2 cores (even those that are only run locally). A lot of back-and-forth about \dontrun{} and \donttest{}. Added \value{} sections in the documentation for various functions. Added further explanation of the "viterbi", "scan1", "scan1perm", etc. S3 classes in the documentation