Make builtin-gconf diagnostics less verbose
Do not ignore mce_conf_init() failures

Previously missing ini files resulted in failure reporting. Since
this is no longer the case, mce should exit if config init fails.
Abort if mce-conf subsystem is used without successful initialization

Now that failing mce_conf_init() causes mce to exit, we can remove
repetitive error handling that deals with NULL keyfile pointers.
Less verbose diagnostics from mce-conf

Since some of the ini-file entries are optional, stop reporting
everything by default as warnings.
Merge pull request #31 from spiiroin/optional_config_warnings

Missing configuration items no longer reported by default