ERT-727: Explicitly initialized logh to NULL.
ERT-727: Added numeric test on log_level

By explicitly checking that log_level > 0 we can instantiate a logh
object on a read only filesystem if we set the log_level to 0 zero.
ERT-727: Changed initialization of log handle.
ERT-727: Moved log_include_message() check
ERT-727: Added logging to time_map update