⚡ enhance genotype conversion

[bunop]

Is your feature request related to a problem? Please describe.
SNP genotype conversion is very slow. For example, if the original file is already in plink binary format it requires too much time to convert it by creating temporary plink text files. Converting the whole dataset into FORWARD (see #111) generates huge temporary files. It requires time converting from binary to text since the information for the same sample is column based in binary and row based in text formats.

Describe the solution you'd like
Ideally data conversion need to be done with binary formats (not text). If it's possible to change only the alleles of the .bim files for plink binary files it needs to be done.

Describe alternatives you've considered
We working with text until now and it's works. However, is very inefficient.

Additional context

• understand how plinkio deal with writing files
• value plink transposed binary format
• value updating only the allele in *.bim file for binary format