adding backbone core

[Gonza10V]

When creating backbones, parts in backbone and plasmids in general the notion of backbone core is useful to refer and mark repeated elements in designs.
For example, in the MoClo kit we have DVA_AE and DVA_AF these are two different backbones that have the same drop-out and backbone core and just differ in the fusion sites. See issue #42

In the Example 1 image we have a promoter part flanked by assembly scars and a backbone core would correspond to the circular glyph.

Example 1

This representations works for circular plasmids but not for linear. Another alternative is to inform the backbone core using regions and leave the circular indicators as context, not referring any component with them, just reflecting the circular type as in example 2 and 3 images.

Example 2

Example 3

I would like to open the discussion and get feedback from the community.

[jakebeal]

I guess that I'm not sure why we really need this, or whether it makes sense. There are often multiple regions of significance on a backbone, including replication, selection markers, and sometimes multiple insertion points. Is this about naming those regions, or is it about naming both them and anything not exactly by the insertion points, or something different?

I also don't see that circular vs. linear actually makes a difference, because in a circular backbone constructs will still often be split across the origin.