test: Streamline test suite a little

This change aims to streamline the integrationtest suite and reduce friction when running (parts of) test suites.

Changes:
- add `test-testname` to makefile to easily run one suite
- made skipping tests first class citizen in test.sh (all available testsuites and the reasons they are skipped are now better exposed and discovered)
- suppress some output of gotest unless there is an error
- no longer build binary for examples and gotest suites
- removed .SILENT from makefile as it being applied to only some targets makes it feel weird (I just learned about this option btw, feel free to comment on this change)
- move individual tests out of `test.sh` and into `test-misc.sh`
- introduced the concept of testsuites to `test.sh`

test/test-commit-message.sh

@@ -1,6 +1,14 @@
 #!/bin/bash -e
+# tests if commit message conforms to convention
 
-echo running test-commit-message.sh
+# library of utility functions
+# shellcheck disable=SC1091
+. test/util.sh
+
+echo running "$0"
+
+ROOT=$(dirname "${BASH_SOURCE}")/..
+cd "${ROOT}" || exit 1
 
 travis_regex='^\([a-z0-9]\(\(, \)\|[a-z0-9]\)\+[a-z0-9]: \)\+[A-Z0-9][^:]\+[^:.]$'