Rework resolver (#489)

* Rework IR and resolver to use nested lookup tables
* Integrate types into IR
* Make components prefer IR, slimmed down AST
* Implement `export *`
* Add `@lazy` annotation and remove `--noTreeShaking`
* Add `@start` annotation and remove magic `main`
* Related refactoring, cleanup and docs

tests/compiler/merge.optimized.wat

@@ -0,0 +1,11 @@
+(module
+ (type $_ (func))
+ (memory $0 0)
+ (table $0 1 funcref)
+ (elem (i32.const 0) $start)
+ (export "memory" (memory $0))
+ (export "table" (table $0))
+ (func $start (; 0 ;) (type $_)
+  nop
+ )
+)