Improves the tool lists in the top-level README.md and in the web home
page:
+ Adds a documentation page for drdisas (#4029) and adds drdisas to
  the tool list.
+ Splits the drcachesim huge page by upgrading each section into a separate
  page.  Renames the top level to make it clear it's a general drmemtrace
  tracing framework and not just a cache simulator.
  Lists the main trace analysis tools separately at the top level.
+ Adds references to 3 external tools: the Arm Instruction Emulator, WinAFL,
  and DrCCTProf.
+ Adds a page for the other samples to the Available Tools menu.

Issue: #4111, #4029
Fixes #4029