Use project folder name for anchors instead of the project titles

[matevz]

Followup to #50 . Having the project URL being extracted from its name has some issues:

• https://playground.oasis.io/#starter-project and https://playground.oasis.io/#starter-project-(go) should be demo-starter and demo-starter-go, because that's what we all call those at the hackathons and discussions. But their project title needs to be more descriptive on Playground, so it's ok to show it as "Starter Project".
• it seems dangerous to allow arbitrary characters as anchors (e.g. https://playground.oasis.io/#texas-hide'em).
• project titles could be duplicated
• some characters (like spaces and maybe some others?) do get replaced by -, so it's not easy to figure out what the anchor will be before trying it out

Let's use the folder name of the project as anchor in the URL based on the folder name and not magically extract it from the project title.