"Cannot find module" message should be more explicit, saying where it's looking

With all the vagaries around module loading, it'd be great to give a more verbose, helpful error message for "Cannot find module 'foo'", saying where the compiler looked for the module. That can help clue the user into (1) how TypeScript works and (2) how to fix their issue.

The message text could be semi-static, maybe something like: IF using commonjs loading AND path isn't relative THEN say "Couldn't find module Foo; searched node_modules directory off directory XXXX and its ancestors and the package.json Typings path YYYY.

Better doc around the module loading algorithm helps, but just putting some of that info in the error message makes it very easily discovered. It also helps clue the user into what isn't the problem (e.g. the message above confirms that using commonjs module loading & found Typings in package.json, but something else seems to be the problem).

Beginne damit, die Beschreibung des Issues zum Laden von CommonJS-Modulen, zur Suche nach node_modules in übergeordneten Verzeichnissen und zu Typings-Pfaden in package.json zu lesen. Verfolge anschließend die Einstiegspunkte für die Modulauflösung und Diagnosen des Compilers und ermittle dann vorhandene Tests für Fehler vom Typ "Cannot find module". Erledigt ist die Aufgabe, wenn die Diagnose erklärt, wo bei der Auflösung gesucht wurde, ohne den ursprünglichen Fehler zu verschleiern.