epicbox version 3.0.0

[johanneshahn]

Refactor epicbox.

Changes:

• Code formatting
• Variable renaming for better code understanding
• Load config with "node app_mongo.js --config /path/to/config.json" else defaults to ./config.json
• Add .gitignore and remove config.json from git index - default config renamed to default_config.json
• Keep backward compatibility to wallet < 3.5.1 and epicbox version 2.0.0
• Rewrite challenge and subscribe logic
• Remove uneccesarry code and logic
• Fix bugs where wallet clients that do not respond get spammed with challenge requests
• standardisation of debug and log messages
• introduce dynamic challenge strings for wallets > version 3.5.1