This is largely an internal change. Prior to this commit, the 'Manifest'
type, now replaced with the 'Cargo' type, robbed responsibility from the
core 'Rocket' type. This new construction restores the previous
responsibility and makes it clear that 'Cargo' is _only_ for freezing,
and representing the stability of, Rocket's internal state.
The directory structure has changed to better isolate crates serving
core and contrib. The new directory structure is:
contrib/
lib/ - the contrib library
core/
lib/ - the core Rocket library
codegen/ - the "compile extension" codegen library
codegen_next/ - the new proc-macro library
examples/ - unchanged
scripts/ - unchanged
site/ - unchanged
This commit also removes the following files:
appveyor.yml - AppVeyor (Rust on Windows) is far too spotty for use
rustfmt.toml - rustfmt is, unfortunately, not mature enough for use
Finally, all example Cargo crates were marked with 'publish = false'.