Liberty Mutual Insurance will soon use drones to photograph houses and businesses damaged by fires or natural disasters for some claims, in place of manned planes or adjusters on ladders. The Federal Aviation Administration last month granted the Boston-based insurance giant permission to use four types of drones of varying sizes, as long as they ascend no more than 400 feet off the ground and travel no more than 100 miles per hour, among other conditions. The drones are relatively small and can’t weigh more than 55 pounds.