Fix stdin control in absence of dbus

Keyboard:
Keyboard reading fully functional even in absence of dbus.
Store last keystroke in member m_action.
New method getEvent() returns and clears it.

OMXControl:
init returns error code -1 if dbus connection fails.

omxplayer:
If OMXControl failed to connect to dbus, read keystrokes directly
from Keyboard::getEvent().

Fixes #62
Fixes #131
Merge pull request #219 from subogero/master

Fix stdin control in absence of dbus
Remove warnings
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
Enable Opus internal audio decoder in ffmpeg
Merge pull request #228 from VittGam/patch-1

Enable Opus internal audio decoder in ffmpeg
Merge pull request #224 from subogero/doc

Generate help and man page from README.md