added units when not present in the label and count of blocking spheres

[danieleongari]

(cleaner than the previous PR https://github.com/ltalirz/aiida-zeopp/pull/39)

[coveralls]

Pull Request Test Coverage Report for Build 244

• 5 of 6 (83.33%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 92.212%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
aiida_zeopp/parsers/network.py	5	6	83.33%
<!--	Total:	5	6	83.33%	-->

Totals
Change from base Build 243:	-0.2%
Covered Lines:	1918
Relevant Lines:	2080

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💛 - Coveralls

[ltalirz]

Closing in favor of #43, which builds on this one.