Accept bond lists

[lilyminium]

Fixes #2373

Changes made in this Pull Request:

• Connections (bonds, angles, dihedrals, impropers) can be instantiated from a list of atom indices
• Values are checked for type and number of atoms
• added tests

Hopefully these checks aren't too slow.

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

[codecov]

Codecov Report

Merging #2379 into develop will decrease coverage by <.01%.
The diff coverage is 75%.

@@             Coverage Diff             @@
##           develop    #2379      +/-   ##
===========================================
- Coverage     89.9%   89.89%   -0.01%     
===========================================
  Files          173      173              
  Lines        21795    21802       +7     
  Branches      2863     2865       +2     
===========================================
+ Hits         19594    19599       +5     
- Misses        1609     1610       +1     
- Partials       592      593       +1

Impacted Files	Coverage Δ
package/MDAnalysis/core/topologyattrs.py	97.53% <75%> (-0.27%)	⬇️

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[richardjgowers]

thanks @lilyminium