JOHNSTOWN — Liberty Restaurant Development cleared a key hurdle earlier this week in its push to open Fulton County's first Popeyes Louisiana Kitchen. The bayou-themed fast-food joint is anticipated to open at some point near the end of this year or the beginning of next year. "They'll do a pretty substantial grand opening for a few days," said Brett Steenburgh, an Niskayuna-based engineer contracted with Liberty Restaurant Development. "Yeah, they tend to do that." Following review from the county, Johnstown city planning officials on Tuesday approved site plans for the 2,532-square-foot restaurant in the North Comrie Avenue arterial area. "It tends…