Split mutable config into global state

[avanaur]

Proposed changes

Resolves #39

Split mutable config data (CurrentMagicBlock, Miners, Shareders) from static config data. Moved the mutable data to a synchronized global state to avoid race condition

Go test race.

(cd code/go/0dns.io && go test -race ./...)
?       0dns.io/core/common     [no test files]
?       0dns.io/core/config     [no test files]
?       0dns.io/core/logging    [no test files]
ok      0dns.io/core/state      0.783s
?       0dns.io/zdnscore/worker [no test files]
?       0dns.io/zdnscore/zdns   [no test files]

Types of changes

What types of changes does your code introduce to 0dns?
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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (no functional changes, no api changes)
• Documentation Update
• Other (Please describe):

Checklist

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• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[cnlangzi]

LGTM