Rename DLE -> DBLab

We're renaming DLE -> DBLab

• in the docs, everywhere
• project name (database-lab, database-lab-engine -> dblab)
• Client CLI remains dblab or we should change it?
  • option 1: rename to dblabctl or similar
  • extend it to control server (install CE or SE/EE, etc.), then it becomes both client and server control CLI
• README.md
• Website beyond the docs