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/switch.optimized.wat

@@ -67,7 +67,7 @@
   end
   i32.const 0
  )
- (func $start (; 3 ;) (type $_)
+ (func $start:switch (; 3 ;) (type $_)
   i32.const 0
   call $switch/doSwitch
   if
@@ -237,7 +237,10 @@
    unreachable
   end
  )
- (func $null (; 4 ;) (type $_)
+ (func $start (; 4 ;) (type $_)
+  call $start:switch
+ )
+ (func $null (; 5 ;) (type $_)
   nop
  )
 )