Move shelter/scan package to shelter/net/scan
Building main service responsable for the scan

See #10
Add comments and exit condition for error listener
Add querier counter for DNSSEC queries too
Limit QPS only in integration test where we repeat domains
Initial structure for scan integration test
Begin tests with the scan service
Closing the log file after usage
Changing querier report to query only a local DNS server, but we
keep the root zone file checking with another option. All other
integration tests have their variables now in configuration files

Resolves #24 #19
Put OK status in the first row
Using common structure for tests
Remove more duplicated code
Query postponed domains because of exceeded QPS and retry timeout connection a number of times before returning an error

Resolves #16 #20
Merge branch 'scan'

Conflicts:
	README.md