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
Merge pull request #224 from subogero/doc

Generate help and man page from README.md