initial api

branch "only" api #5 (closed)

• /api/{packages,applications,snaps}/ for list
• /api/{packages,applications,snaps}/"packagename" for detail

Content-Type: application/json

format:

{
"count":1,
"items":[
    {"app-name":"VLC",
     "builddate":1582372025,
     "conflicts":["vlc-plugin"],
        ...
     }
],
"status":200,
"title":"Packages"
}