(Fix) Registry with events for testnets, fix in stats

[vbaranov]

• Registry with events for networks: Kovan, Rinkeby, POA Sokol, POA Core
• Fix bug in stats: contributors and wei raised are accounted twice due to joinedCrowdsales consists of all tiers.

[coveralls]

Pull Request Test Coverage Report for Build 2213

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 22.164%

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Totals
Change from base Build 2199:	0.005%
Covered Lines:	651
Relevant Lines:	2562

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💛 - Coveralls