Rework AJXP_Logger to expose all log levels

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>
Add logging functions to AJXP_Plugin class / put plugin id as log prefix

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>
Rework auth.ldap logging

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>
Replace all 'AJXP_Logger::logAction("error"' with 'AJXP_Logger::error('

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>