Support configuring a custom function with the request object as an input param for URL pattern

[liuruoran88]

sw-toolbox has two options, Express-style Routes and Regular Expression Routes, for configuring the routes, but it's not flexible enough for users. If it can support configuring a custom function with the request object as an input param for url pattern，users can do more processing according to the request object. In order to meet this need, I have changed two files, lib/router.js and lib/route.js, and added some test cases in the test folder. These changes will not affect the original Routes config.Your prompt attention to this matter will be appreciated.

An example of using Function Expression routing include:

toolbox.router.get(
function(request){
  // users can get request object, do some processing accroding to the request object and return a boolean value
  if (request && reqest.headers && request.headers.referer) {
     return true;
  } 
}, apiHandler);

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[liuruoran88]

I signed it!

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[liuruoran88]

ok, I have committed another new PR, please check again, thank you!