Allow to include user defined routes

[php-coder]

There should be a way to include custom routes. I see at least 2 ways:

• enhance DSL to have parameters for specifying file names to include
• use Convention Over Configuration approach where we include all files named *_routes.{ext} automatically if they exist

Plan:

• js
• ts
• go
• python

[php-coder]

Should be done after #28