move the man pages to the docs/ dir

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Fix search integration-cli test

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6629 from SvenDowideit/move-man-pages-to-docs

move the man pages to the docs/ dir
Merge pull request #6654 from vieux/fix_test_search

Fix search integration-cli test
refactor TruncIndex to use a trie & vendor deps

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)