Allow chain id to be assigned with chainid!()

[gusennan]

Adds two function for assigning the chainid, chainid!(chain, new_id) and chainid!(residue, new_id).

For issue #22

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    It's nice to be able to programmatically modify structures.

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    I added some unit tests.

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[jgreener64]

Thanks for trying this, I agree it is not easy.

What you have is a start but it is also important to update the key in the chains Dict of the Model that owns the Chain, otherwise mod[new_chainid] won't work.

I think there should be a new error type, something like PDBConsistencyError, which is thrown if you try to rename something to an already existing name (e.g. the new chain ID already exists in the model or the residue ID already exists in the chain it is moved to).

[gusennan]

Thanks for the comments. I agree with your ideas. I've pushed a new commit I think addresses these shortcomings.

[codecov]

Codecov Report

Merging #35 (7b84144) into master (d1fc832) will increase coverage by 0.06%.
The diff coverage is 100.00%.

❗ Current head 7b84144 differs from pull request most recent head c892e5a. Consider uploading reports for the commit c892e5a to get more accurate results

@@            Coverage Diff             @@
##           master      #35      +/-   ##
==========================================
+ Coverage   95.29%   95.36%   +0.06%     
==========================================
  Files           6        6              
  Lines        1553     1575      +22     
==========================================
+ Hits         1480     1502      +22     
  Misses         73       73              

Impacted Files	Coverage Δ
src/model.jl	96.15% <100.00%> (+0.16%)	⬆️

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[jgreener64]

Thanks for making those changes. Just a few minor things and this is ready to merge.

[gusennan]

@jgreener64 made those changes.

[jgreener64]

Great, thanks for the contribution!