Added and optimized some log item types

Added and optimized some log types
Maybe a seperate (oxygen theme) icon should be created for log types LOG_ISSUE_PAIN_BUG_TYPE, LOG_ISSUE_PAIN_EFFECT, LOG_ISSUE_PAIN_LIKELIHOOD and LOG_ISSUE_PAIN_CALCULATED, see file _issuelogitem.inc.php lines 226, 235, 244, 253