Improve logging options

[renefloor]

✨ What kind of change does this PR introduce? (Bug fix, feature, docs update...)

feature

⤵️ What is the current behavior?

Currently there is no way to determine the detail of the logs. It always shows failed downloads.

🆕 What is the new behavior (if this is a feature change)?

The new logger can decrease or increase the amount of logs.

💥 Does this PR introduce a breaking change?

No

🐛 Recommendations for testing

📝 Links to relevant issues/docs

Fixes

• Add log settings to show/hide download errors flutter_cached_network_image#351

🤔 Checklist before submitting

• All projects build
• Follows style guide lines (code style guide)
• Relevant documentation was updated
• Rebased onto current develop

[codecov]

Codecov Report

Merging #350 (d14bfa3) into develop (101c6a1) will increase coverage by 0.17%.
The diff coverage is 73.33%.

@@             Coverage Diff             @@
##           develop     #350      +/-   ##
===========================================
+ Coverage    75.21%   75.39%   +0.17%     
===========================================
  Files           21       22       +1     
  Lines          682      691       +9     
===========================================
+ Hits           513      521       +8     
- Misses         169      170       +1     

Impacted Files	Coverage Δ
...cache_info_repositories/cache_info_repository.dart	94.11% <0.00%> (ø)
flutter_cache_manager/lib/src/cache_manager.dart	88.31% <60.00%> (ø)
flutter_cache_manager/lib/src/logger.dart	80.00% <80.00%> (ø)
flutter_cache_manager/lib/src/cache_store.dart	92.55% <100.00%> (+0.16%)	⬆️
flutter_cache_manager/lib/src/web/web_helper.dart	95.65% <100.00%> (+0.09%)	⬆️

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