New option -I --with-info

Add new option -I --with-info to dump media format before playback,
besides old -i --info which dumps media format instead of playback.

Implements #220
Merge pull request #221 from subogero/always-dump

Always dump format
Generate help and keybindings from README.md #223
Generate man page from README.md #223
Makefile cleanup #223

Makefile:
Rule dist became main target, no more a prerequisite to install.
Reason: install is run as root, avoid creating root-owned subdir in workdir.

prepare-native-raspbian.sh:
Add removal of manpage to uninstall rule.
README.md warning about being source itself #223