This patch:
  - introduces the dynamic checking that fields in the result table row
    for INSERT statement don't have default value or
    isn't set inside BEFORE-trigger;
  - adds uniform approach to handling warnings/errors if some fields are missed
    from INSERT statement and these fields doesn't have default values;
  - handles possible missed fields and set error in Diagnostic_area if
    strict_mode is set and IGNORE isn't set in INSERT statement; 
  - modifies guint tests: replaces explicit assignement of pointer value to
    Field::m_null_ptr by call of Field::set_null_ptr();
  - adds tests for wl6030.