Misc07 cleanup multipletesting and proportions

first part: some cleanup of multipletesting, 
    see also http://jpktd.blogspot.ca/2013/04/multiple-testing-p-value-corrections-in.html
    closes #763
    closes #764
    closes #766

second part: statistical test for proportions and normal based tests
still WIP
some functions still miss unit tests
currently all written as individual functions, 
     maybe add a class to collect methods, add plotting ?
     and more results classes
     the allpairs tests return a results instance, all others just numbers
some functions are still missing (ztest_prop, with more options than generic ztest)

adding ztest and ztost to weightstats is incomplete (not attached as methods)