Add journald logging and refactor log system

Add journald logging and refactor log system

Add journald log provider. Simplify log system and log providers. Add support
for environment flags.

[Verification] Compile and run different build configurations with different
CKM_LOG_LEVEL and CKM_LOG_PROVIDER values. For client apps just export desired
log level/provider as CKM_LOG_LEVEL/PROVIDER env variable and run it. For ckm
service use:

'echo "CKM_LOG_LEVEL=X" > /etc/sysconfig/central-key-manager'
'echo "CKM_LOG_PROVIDER=X" >> /etc/sysconfig/central-key-manager'

and restart ckm service.

Supported CKM_LOG_LEVEL values: <0,5>
Supported CKM_LOG_PROVIDER values: {CONSOLE, DLOG, JOURNALD }

Observe logs.

1.Release build
 -by default (CKM_LOG_LEVEL not set) only errors should be logged
 -by default (CKM_LOG_PROVIDER not set) dlog is used
 -logs can be disabled completely by setting CKM_LOG_LEVEL to 0
2.Debug build
 -by default Debug and higher severity logs should be logged
 -by default (CKM_LOG_PROVIDER not set) dlog is used
 -log level can be adjusted to any level <0,5>

Change-Id: I496d12309360354399cf5011680f081ce42ee58f