TRC fetcher

[tzaeschke]

Fetch and parse trc metadata (json files) from bootstrap server.

[codecov]

Codecov Report

Attention: Patch coverage is 86.47059% with 23 lines in your changes missing coverage. Please review.

Files	Coverage Δ	Complexity Δ
src/main/java/org/scion/jpan/ScionService.java	66.66% <87.50%> (ø)	50.00 <1.00> (ø)
...rc/main/java/org/scion/jpan/internal/Segments.java	68.01% <92.85%> (-14.15%)	65.00 <9.00> (ø)
...ava/org/scion/jpan/internal/ScionBootstrapper.java	79.77% <80.00%> (-0.23%)	21.00 <5.00> (+5.00)	⬇️
...n/java/org/scion/jpan/internal/GlobalTopology.java	83.95% <83.95%> (ø)	17.00 <17.00> (?)

... and 1 file with indirect coverage changes