Added symbols

[dr3y]

I have added some symbols and changed a bit how the recombinase symbol is shown so that it makes a bit more sense (color1 and color2 always represent the left or right half of the split triangle, rather than flipping when you draw it in reverse) Edit: new symbols are:

• aptamer
• ncRNA
• oriT

[chofski]

There seems to be a conflict with master. Could you update to fix this and then I'd me happy to accept.