CSV file handling: single space now treated as NA

CSV files written by SPSS have single spaces for missing values
Fixes to t-tests
Bayesian ANOVA: temporary hiding of options

until the appropriate R code is working
Fixes to missing values in NominalText variables
Removed JASP R package imports

they cause some problems on some machines
ANOVA: Fix to text alignment

Fixes #30
ANOVA: Fixed blank table to match final
RM ANOVA: added grey lines to delineate sections