Fix schema accidently strings values to correct integers

[jfy133]

This is to close #654 . It makes sures all integers defaults are actually integer values and not accidently in strings. It also adds an a enum for bt2n as acoording to bowtie2 docs can only be either 0 or 1.

This should hopefully fix launch GUI params.json issues during internal eager parameter validation

PR checklist

• This comment contains a description of changes (with reason).
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[apeltzer]

Looks good to me :-)