Miscellaneous bug fixes.

This version includes miscellaneous bug fixes, error-handling, and corrections to the documentation.

• Wald_test() gains an option for test = "Naive-Fp", which uses denominator degrees of freedom equal to the number of clusters minus the number of coefficients in the fitted model.
• coef_test() and conf_int() gain an option for test = "naive-tp", which uses denominator degrees of freedom equal to the number of clusters minus the number of coefficients in the fitted model.
• Corrected a bug in the Satterthwaite degrees of freedom calculations for models that include only an intercept.
• Output of coef_test() and conf_int() now include a variable containing the coefficient names, so that the results are "tidy."
• conf_int() now includes an option to report a p-value for each coefficient.
• coef_test() now reports degrees of freedom for test = 'z' and test = 'naive-t'.
• vcovCR() now provides a more informative error message when the clustering variable is a constant.
• vcovCR() now handles models estimated using analytic weights, where some weights are equal to zero. Results are consistent with omitting observations with weights of zero.
• Added more informative error messages for Wald_test() and conf_int(), triggered if the test argument does not match any of the available tests.
• Corrected a bug in findCluster.rma.mv(), which threw an error if a random effects factor in the rma.mv model had unobserved levels.
• Corrected a bug in Wald_test(), which threw an error for tests of intercept-only models.
• Fixed a minor bug in print method for Wald_test() results, which threw an error when the p-value was NA.