Add custom file format for simplecov coverage type

[SokolAndrey]

Most of the repos I checked use this format for coverage files.
Which is something between the legacy and new version.
The main differences that this format has:
 - there is no metadata fields;
 - it contains high level name, which can be configured by the users;
 - it uses lines and branches primitives (same as the new version).

[CLAassistant]

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❌ psarna
❌ glkz
❌ SokolAndrey
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[codeclimate]

The PR diff size of 610249 lines exceeds the maximum allowed for the inline comments feature.

[codeclimate]

Code Climate has analyzed commit 34fa698 and detected 4 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	1
Duplication	2
Bug Risk	1

View more on Code Climate.