Fixes to image rendering

Single images would not re-render when resized.
Updates to the R bundle

- OSX bundle updated to R-3.1.1
- Bundles updated to Rcpp 0.11.3
- Bundles now include qgraph, lme4, etc.
Fix to DataSet loading crash

loading certain data sets would crash JASP
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