Dependency rework

[SquidDev]

Currently the dependency system is rather susceptible to breaking, especially on mappings: they tend to send it into an infinite loop. Some tasks do not correctly set the outputs or inputs or do not gather all inputs, resulting in a fairly limited system. Ideally we would be able to have:

• Breadth first search of dependency tree
• Sources capture outputs of other tasks: *.lua could capture the output of other tasks. It might be possible to have *.min.lua use a mapping task to minify a source set. We would have to see.

It might also be nice to detect whether dependencies have changed or not and so have some form of incremental compilation.