RWeka != farff when a feature contains only FALSE

[giuseppec]

Suppose this is my data:

@relation R_data_frame

@attribute V1 {FALSE}
@attribute V2 {FALSE,TRUE}

@data
FALSE,TRUE
FALSE,FALSE

Reading this data with RWeka gives me:

'data.frame':	2 obs. of  2 variables:
 $ V1: logi  FALSE FALSE
 $ V2: logi  TRUE FALSE

while farff does not recognize the first feature as logical but as a Factor:

'data.frame':	2 obs. of  2 variables:
 $ V1: Factor w/ 1 level "FALSE": 1 1
 $ V2: logi  TRUE FALSE

[berndbischl]

merged in #33