core: Make AuditLog more Java coding conventions friendly

1. Refactor constructors to make proper constructor chaining
2. Rename getter/setter acording to Java coding conventions
3. Code cleanup (remove unnecessary brackets, simplify, ...)

Change-Id: Idbc05cd0006737d8ff0c923ab2b6aae18389de90
Signed-off-by: Martin Perina <mperina@redhat.com>