feat: env var STORE_DIR and renamed OZW_NETWORK_KEY to NETWORK_KEY

[robertsLando]

Fixes #85

[coveralls]

Pull Request Test Coverage Report for Build 501586574

• 106 of 180 (58.89%) changed or added relevant lines in 8 files are covered.
• 7 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.4%) to 23.326%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
app.js	0	1	0.0%
lib/ZwaveClient.js	0	2	0.0%
lib/MqttClient.js	0	11	0.0%
lib/utils.js	82	142	57.75%

Files with Coverage Reduction	New Missed Lines	%
lib/logger.js	1	85.35%
lib/Gateway.js	3	17.81%
lib/utils.js	3	62.43%

Totals
Change from base Build 501298160:	0.4%
Covered Lines:	2000
Relevant Lines:	8776

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💛 - Coveralls