initial version of tile seeder
added README.md for tile_seeder, cleanups in the code itself
geoserver/tile_seeder: hardcoded values for default bbox revmoed
wrapping tile_seeder.js with layer_seeder.sh
layer_seeder improvements

 * removed logic from tile_seeder.js and moved to layer_seeder
 * layer_seeder can run requests concurrently, speeding things up
 * proper command line parameter handling for layer_seeder
Merge pull request #9 from aodn/tile_seeder

Tile seeder