Fix version and download paths in docs config
[docs] Various fixes in docs
  - corrected links to download page
  - corrected download urls
  - corrected wget shortcut for yarn setup
  - corrected links to faq in yarn setup
  - corrected guide for manual yarn build
  - FAQ layout
Another round to remove final modifier to private methods because it is not needed

Remove final modifier to private methods because it is not needed.
Those methods are final by default.

Author: Henry Saputra <henry.saputra@gmail.com>

Closes #168 from hsaputra/remove_final_privatemethods_1 and squashes the following commits:

860b512 [Henry Saputra] Remove final modifier to private methods because it is not needed. It is final by default.
[FLINK-1203] Deactivate fork reuse in tests (workaround for potential surefire bug)
[FLINK-1202] Remove incomplete file outputs on failure