Rename crates to something more descriptive

[insipx]

the plan is to rename the core, core_v14, and possibly extras crate to better reflect their roles in the codebase. It should be kept in mind that at some point there will be a facade crate that ties what currently is core and core_v14 together.

my suggestion is:

• rename core to legacy
• rename core_v14 to core
• facade name is ??? (something cool maybe, maybe just desub?, desub-typeinfo?)

facade will be the crate that has the latest metadata decoding enabled by default, and then will have features that enables legacy decoding as well.

[jsdw]

core => desub-legacy
core_v14 => desub-current
facade => desub
extras => desub-json-resolver

I think was suggested in our chat :)