* Declare used properties in constructor
* Module.(re)building moved into Compilation._(re)buildingModules (Map)
* Make NormalModule.error private
* Move Module.cacheable logic into needRebuild
* More stable implemention of rebuildModule
* addModuleChain waits for Module building finished before returning
* Set built and cacheable flags correctly in Modules
* More portableId into WeakMap
* Add ModuleReason for entrypoints
* cacheable can be true/false/null in Stats
* added Stats module issuerPath
* fixes profile in stats output
Fixes an issue where multiple calls to loadModule from within a loader
would resolve modules using the context of the *last loaded module*
rather than the module *doing the loading*, which is problematic if the
modules being loaded are in different directories.