Updates to Concepts

[raychu86]

A couple outdated things in the current docs that I noticed need some updating to support the current model (in no particular order):

• "gates" has been renamed to "microcredits" and is only allowed in credits.aleo records.
  • The example in the Programs seconds also need to be updated - https://github.com/AleoHQ/welcome/blob/0e7c1556a18f8400d4d09ba79237c1a0d7d0d6e7/documentation/concepts/01_programs.md?plain=1#L27
• Transactions
• Transitions now do not have proofs (as they are batched into the execution proof)
• Block headers and metadata now have additional fields
• New fee model is in place for finalize, deployments, etc.
• Concept of finalize needs to be added