[improvement] better map builder

Hey there I'm just working on a better/faster way to create maps in challenges und I came up with the following solution:

it's much faster to write a map like this:

```` lua
local _map = {
  {1,2,0,1,1,1,0,1,1,1,},
  {1,2,3,1,4,1,0,1,2,1,},
  {1,2,1,1,1,1,0,1,1,1,},
  {1,0,1,0,0,1,0,0,0,1,},
  {1,1,1,1,1,1,2,1,0,1,},
  {1,0,0,0,0,0,1,1,0,1,},
  {1,1,1,1,1,1,1,1,1,1,}
}
````
with the convention to interpret `1 as 'C'`, `2 as 'H'`, `3 as 'S'` and `4 as 'STORE'` one can easily 'design' maps.

the convert-code should then be something like:

````lua
function challenges.convertTableToMap(table)
  local map = {}
  local _mapAssoc = {}
  _mapAssoc[0] = nil
  _mapAssoc[1] = "C"
  _mapAssoc[2] = "H"
  _mapAssoc[3] = "S"
  _mapAssoc[4] = "STORE"

  for i,row in ipairs(table) do
    for j,value in ipairs(row) do
      if value > 0 then
        map[j][i] = _mapAssoc[value]
      end
    end
  end
  return map
end
````