Configurable DNS search domain

[tzaeschke]

Add environment variable / property to specify DNS search domain

[codecov]

Codecov Report

Attention: Patch coverage is 52.38095% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...c/main/java/org/scion/jpan/internal/DNSHelper.java	56.25%	5 Missing and 2 partials ⚠️
...in/java/org/scion/jpan/internal/PathRawParser.java	0.00%	3 Missing ⚠️

Files with missing lines	Coverage Δ	Complexity Δ
src/main/java/org/scion/jpan/Constants.java	100.00% <ø> (ø)	1.00 <0.00> (ø)
src/main/java/org/scion/jpan/ScionService.java	66.54% <100.00%> (+0.24%)	51.00 <0.00> (ø)
...in/java/org/scion/jpan/internal/PathRawParser.java	65.85% <0.00%> (ø)	13.00 <0.00> (ø)
...c/main/java/org/scion/jpan/internal/DNSHelper.java	71.25% <56.25%> (-2.67%)	21.00 <14.00> (+1.00)	⬇️