v0.005
-first usable version
-has 'load/save maps' commands
-has 'change tileset' command
-can zoom/unzoom with mousewheel or keys +/-
-can slide map with right mouse button
-can put tiles and remove them
-fileformat for maps:
 .tiles are coded on one byte from 0 to 254
 .255 means unset
 .encoded in the file by scanning every line from left to right,
  starting from the topmost line
 .only 16x16 maps are available (now)
-fileformat for tilesets:
 .plain png image
 .number of rows, cols, size of tile, and separation interval are not encoded
  in the file: the user has to input them (now)

v0.006
-minor user interface changes
-a bug fix
 (added index not out of bound check when querying a tile in the tileset,
  during the painting of the screen; added a similar check when loading a new tileset)

v0.007
-added a 'change map dimensions' command
 It changes nb of rows and cols of the map
-chaged the map fileformat: width and heigt are now encoded in the firt 8 bytes

v0.008
-added an undo (shift Z, shift Y)
-added 'insert map' command
-added 'change background' command 
 (cycles through lt gray, dk gray, black)

v0.009
-solved the focus loss when dialog closes
 (by adding requestFocusInWindow() after disposal)