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`

README.md

@@ -41,6 +41,7 @@ Please read, enjoy and help improve our documentation!
 | [godoc API reference](https://godoc.org/github.com/purpleidea/mgmt) | for mgmt developers |
 | [prometheus guide](docs/prometheus.md) | for everyone |
 | [puppet guide](docs/puppet-guide.md) | for puppet sysadmins |
+| [development](docs/development.md) | for mgmt developers |
 
 ## Questions:
 Please ask in the [community](#community)!