Sample-tester

This captures more details about the v0.11.0 release

This release introduces version 2 of the manifest file schema, which happens to be a superset of version 1. This version adds support for tag inclusion via the format `{TAG_KEY}` in tag values.

The sample tester now also
* interprets the manifest key `invocation` (the name of the key can be overriden) to specify how to run the artifact, and within the corresponding value, it interprets the literal `args` as the location in which to insert the arguments to the sample
* interprets the the manifest key `chdir` (the name of the key can be overrriden) to specify the working directory when running the sample.

**Semantic change**: Use `sample` instead of `target` in testplan files

Functional changes:
* **SEMANTIC CHANGE**: change tag convention to use `environment` and `sample` (31) by default (the latter can be overridden at run-time)
* implement `extract_match` to retrieve regexps from call output (27)

Other changes:
* stricter semantics on `call` vs `shell` (25 29)
* make `_last_call_output` available via yaml and code (30)
* print failing suite name (26)
* assorted clean-ups

Fixes: assertions abort, ^C handled, skipped tests work, safer YAML loading