fix: recompile moved contracts

[matnad]

What I did

Fixed FileNotFoundError when moving a contract source file.

Closes #539

How I did it

Delete artifacts where no matching source is found and recompile the artifact.

How to verify it

Move a contract to a different folder and compile the project, then check the new artifact.

Checklist

• I have confirmed that my PR passes all linting checks
• I have included test cases
• I have updated the documentation
• I have added an entry to the changelog

[codecov-commenter]

Codecov Report

Merging #545 into master will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #545      +/-   ##
==========================================
- Coverage   88.43%   88.39%   -0.05%     
==========================================
  Files          56       56              
  Lines        6279     6282       +3     
  Branches     1387     1388       +1     
==========================================
  Hits         5553     5553              
- Misses        496      498       +2     
- Partials      230      231       +1     

Impacted Files	Coverage Δ
brownie/project/main.py	89.52% <0.00%> (-0.62%)	⬇️

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[iamdefinitelyahuman]

👍