Better error handling

--force now lets script run its course with warnings, instead of stopping on first error
        User will be notified about problems (missing files, missing repositories, etc.)
Fixed typo
Better --checksum handling

Now script returns error code only if user specifies '--quiet' option.
Without it, script returns "Checksum OK" or "Checksum changed" without error code,
which should allow for better handling in Ansible (no alarming error messages)