New JWT Middleware features and more

[kataras]

• New JWT features and changes (examples updated).
• Improvements on the Context User and Private Error features.

Relative to:

• [FEATURE REQUEST]get username from http basic auth and other types of auth iris-contrib/middleware#63

TODO:

• Think, design and write the code
• For the sake of performance, I had to design our own jwt parser
• Add tests
• Update examples
• Add a tutorial
• In-memory and Redis Blocklist
• Write the new e-book JWT section
• Write the HISTORY entry
• Add a simple example on site docs