Gbpcli

Add functionality to allow gentoo-build-publisher to upgrade to 1.5.x

A lot of internal improvements. User-facing changes include:

- Add ability to search the logs
- Add help text for the --my-machines flag

Notable changes of this release are:

* Theme support
* A new `inspect` subcommand
* The `--my-machines` flag and `GBPCLI_MYMACHINES` environment variable.

Minor release to give better usage text.