Fix : remove cache issues for css, js, templates

Packaged css and js are now suffixed with the build date.
All templates are exported to a folder named after the build date.
Streamlined the build process to copy files to piskel-website.

Isolated common part between piskel and piskel-website in a separated
template, which is now completely created by the grunt build of piskel.

Added a windows CMD script to copy the static resources to piskel-website.
Fixed IE issues + verisoning for iframeloader and boot
swap color : initial implementation
Fix selection paste transparent pixels
perf step 1 : ok on chrome,horrible on FF
Removed unused methods from Frame
Settled on temp icon for swap colors
Settled on temp icon for swap colors
Removed hack from ColorPicker class
Improve tooltip design
Refactoring tooltip code + display CMD on mac
Cleanup of tooltip generation
Merge pull request #203 from juliandescottes/feature-swap-color

Feature swap color
Image dnd first implementation
Merge branch 'master' into feature-export-to-file
Merge branch 'feature-dnd-images' into feature-export-to-file
Create 2 new dialog controllers

Image import is now triggering a popup after selecting the file.
Same for local saves.

Drag and drop of .piskel files opens the piskel immediately !

Remains to do :
- redesign the dialog for import image and browse local
- create dialog for recover session
- improve recover session to handle more than the last session