* add my own build key
* enable the repo in the config
* update the README file
* Adjust testcase, that validates the keys and enable it in testcases_fast.sh
* Only save/load keys to/from the config file, which we ask for during
'pmbootstrap init', so the binary repo gets used even if a config file
already exists (this also removes a workaround, that deletes the work
folder path from the config dictionary before writing it)
* Download missing APKINDEX.tar.gz files with Python code, before
attempting to build packages (so we know which ones aleady exist in
the binary packages repository)
* Consider APKINDEX files older than 4 hours as outdated and download
them again (also in Python code)
* Provide 'pmbootstrap update' to force-update the APKINDEX files
* Travis: more logging output on failure
* Only allow keys from config_keys to be used by "pmbootstrap config"
Oliver Smith