The fire that ravaged a historic house at West Seventh Street and Kenilworth Avenue in Lansdale earlier this week has been ruled accidental.   Fire Marshall Jay Daveler says a woman living there put hot ashes from a fireplace into a cardboard box on the porch.   She suffered an anxiety attack on the scene and was taken to the hospital but no one else was injured.   The blaze caused almost $600,000 in damages.   The owner of the house says it is the oldest one in Lansdale.