fixes #219
Merge pull request #220 from andygup/fix_sample_onlineoffline

Minor fix appcache-features sample
initial commit of TilesCore.js
refactored _storeTile() to TilesCore
refactored parseGetTiledInfo to TilesCore
added additional image type detection
console logging of errors now works correctly
removed unused code
added spatialReference to the Extent
more tweaks to error messages
removed unused callback value
switched to deferred promises in _parseInMemFiles()
fixed minor firefox bug
updated TPKLayer how to use doc
Merge pull request #224 from andygup/detect_png

Add addt'l tpk image type detection
Merge branch 'master' into consolidate-tile-core
refactored getTilePolygons to TilesCore
refactored loadFromFile() into TilesCore
refactored estimateTileSize() into TilesCore
refactored saveToFile() to TilesCore