Allow setting boot, wiki, and pathPrefix for each request (#4649)

* Add pathPrefix to state, and options to request handler

* use ternary operator instead of default empty object

* Fix styling issues

* Update server.js

* Add boot to server and filesystem adapter

core/modules/server/routes/get-file.js

@@ -21,7 +21,7 @@ exports.handler = function(request,response,state) {
 		fs = require("fs"),
 		util = require("util"),
 		suppliedFilename = decodeURIComponent(state.params[0]),
-		filename = path.resolve($tw.boot.wikiPath,"files",suppliedFilename),
+		filename = path.resolve(state.boot.wikiPath,"files",suppliedFilename),
 		extension = path.extname(filename);
 	fs.readFile(filename,function(err,content) {
 		var status,content,type = "text/plain";