Documentation updates

[atodorov]

Most importantly:

• document how external bug trackers are integrated within Kiwi TCMS and how they need to be configured
• document how to organize the testing workflow and how to answer common questions related to reporting.

[coveralls]

Coverage increased (+0.003%) to 59.355% when pulling da219aa on next_release into c392c88 on master.

[coveralls]

Pull Request Test Coverage Report for Build 343

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.003%) to 59.355%

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Files with Coverage Reduction	New Missed Lines	%
tcms/issuetracker/types.py	1	29.69%

Totals
Change from base Build 338:	0.003%
Covered Lines:	7165
Relevant Lines:	11267

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💛 - Coveralls