Add `loglogistic`, `logitexp`, `log1mlogistic` and `logit1mexp` #336

Job	Run time
Documentation	1m 3s
Julia 1.0 - ubuntu-latest - x64 - pull_request	5m 15s
Julia 1 - ubuntu-latest - x64 - pull_request	3m 46s
Julia nightly - ubuntu-latest - x64 - pull_request	4m 21s
	14m 25s

Provide feedback