fix row splitting

[rdmorin]

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• I ensured not to prepend the functions existing in both GAMBLR.data and GAMBLR.results with <package>::function() syntax.
• I ensured not to add GAMBLR.data or GAMBLR.results to the @import section of the documentation

[lkhilton]

Please see this PR for accompanying changes. I ensured that the colours in the oncoplot match the right barplot, and retained factor levels of the input splitGeneColumn argument.

[Kdreval]

Thanks everyone!