Change attachment points of backbone monomers in automatically created antisense chains

[ljubica-milovic]

Background
Both sense and antisense chains are characterized by a free R1 of the sugar on the 5' end, and a free R2 of the sugar on the 3' end.
In the scope of this ticket, the logic for creating antisense chains should be improved by changing the attachment points of backbone monomers.

Requirements

1. For any backbone connection between R1 of monomer A and R2 of monomer B in the sense chain, on the antisense chain the bond should be established between R2 of monomer A* and R1 of monomer B*.

2. The terminal indicator of the antisense chain 3' should be placed on the left-most sugar (and C on the left-most amino acid) of the chain.

Both for automatically created antisense chains with reversed APs, and in the case that the user draws such chains manually.

3. The numbering of monomers should start from the right.

Side marked with the terminal indicator should be associated with the largest number.

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Current behavior:

If APs get changed manually:

Behavior described in this ticket: