Library restructure (#104)

* Move wasmer-runtime to wasmer-runtime-core

* Add the runtime library

* Fix issue with macros using wasmer_runtime, fmt

* Make default compiler dependency optional

* Add instantiate and validate functions

lib/clif-backend/src/lib.rs

@@ -12,7 +12,7 @@ use cranelift_codegen::{
     settings::{self, Configurable},
 };
 use target_lexicon::Triple;
-use wasmer_runtime::{
+use wasmer_runtime_core::{
     backend::{Compiler, Token},
     error::{CompileError, CompileResult},
     module::ModuleInner,