BiasCorrection() memb_dim does not function well

Reported by @jramon, BiasCorrection() parameter memb_dim doesn't work as expected. The bugs lie in the lines that use "member" rather than memb_dim. For example, (see line number here)

(line 44)
if (dim(obs$data)['member'] != 1) {

(line 176)
names(dim(corrected)) <- c('member', 'sdate')  #'sdate' need to be changed too

(line 187)
names(dim(corrected)) <- c('member')

@erifarov can you take care of this issue? Thanks.

Best,
An-Chi