More slip mutation modes

[amlalejini]

Changes:

• Minor code clean up in the doSlipMutation function
• Implement slip mutation mode like slip-random but random instructions drawn from genome instead of the full instruction set
• Implement slip mutation mode like slip-scatter but instead of inserting random instructions, insert the instructions from the would-be duplicated sequence
• Implement slip mutation mode like slip-duplicate but the duplicated sequence is inserted at a random location in the genome instead of directly after the original sequence