Asset Pack Refactor

[GoodBoyDigital]

Pretty much wrapped up this refactor, its quite a biggie!

Summery of changes

Renamed plugins to pipes. Assets now flow from pipe to pipe in the order that they are instantiaed. An asset can go through a pipe and be transformed - those transformed assets will then continue through to the other pipes and subsiqently be transformed. Until we get to the end of the pipes, at that point things are copied to the out put folder.

• this means an assets journey, does not depend on any other assets journey, so can be done synchronously
• we maintain a transformation chain so we know where an output asset originated, making it much easier to build things like manifests.
• replaced 'tags' with metadata. this is a more general term, tags still exist - but they serve a purpose of attaching info to metadata. This way other channels can modify the metadata too.
• added a progress bar to show visual progress and complement our spinner
• added support for compression of sprite sheets
• add support for sprite sheet shortcuts
• added a cache.

Next steps

• not tested in windows - it should be ok as i have used 'safe' versions of upath where possible and not done any path manipulation myself.
• we need a faster texture packer. this is choking astro right now!
• need to tweak the loggin, its not quite right yet!
• add a skip or copy tag that will copy the thing and not transform the asset