Prepare docs for 3.0.0

[DavidBadura]

• readme improve readme, index and getting started docs #440
• aggregate improve aggregate, clock, event bus and message decorator docs #483
• aggregate id improve aggregate, clock, event bus and message decorator docs #483
• cli remove optional dependency and add required doctrine migration #505
• clock improve aggregate, clock, event bus and message decorator docs #483
• message Message docs #564
• event bus improve aggregate, clock, event bus and message decorator docs #483
• events improve aggregate, clock, event bus and message decorator docs #483
• getting started improve readme, index and getting started docs #440
• index improve readme, index and getting started docs #440
• message decorator improve aggregate, clock, event bus and message decorator docs #483
• normalizer upgrade hydrator & use new auto detect feature #510
• projection overhaul projectionist #503
• repository update repository, snapshots, split stream and upcast docs #507
• snapshots update repository, snapshots, split stream and upcast docs #507
• splitstream update repository, snapshots, split stream and upcast docs #507
• store remove optional dependency and add required doctrine migration #505
• tests update repository, snapshots, split stream and upcast docs #507
• upcasting update repository, snapshots, split stream and upcast docs #507