add docs for mendel errors
add docs for mendel errors

bgruening/gemini,bgruening/gemini,xuzetan/gemini,udp3f/gemini,arq5x/gemini,udp3f/gemini,arq5x/gemini,brentp/gemini,bw2/gemini,heuermh/gemini,heuermh/gemini,bgruening/gemini,udp3f/gemini,bpow/gemini,xuzetan/gemini,brentp/gemini,brentp/gemini,bw2/gemini,arq5x/gemini,bw2/gemini,heuermh/gemini,bw2/gemini,brentp/gemini,heuermh/gemini,xuzetan/gemini,udp3f/gemini,bpow/gemini,bgruening/gemini,bpow/gemini,bpow/gemini,xuzetan/gemini,arq5x/gemini