Improve conan install with RREV usage

The revision feature is the safest way reproduce and use a very same package from machine to machine. So far, we have it documented here: https://docs.conan.io/en/latest/versioning/revisions.html#how-it-works

However, if I want to use it associated to conan install command (https://docs.conan.io/en/latest/reference/commands/consumer/install.html) it's not clear how to execute together, the main option now is using lockfiles.

For instance:

conan install jsoncpp/1.9.5@#536d080aa154e5853332339bf576747c:b5855232fa6dee7d27d2005b789408c1c12da382 -r conancenter

We know this is invalid, but we don't have a reference for valid cases.

I suggest updating `conan install` section with a new section explaining revisions support.

Read the revisions documentation at docs.conan.io/.../versioning/revisions.html#how-it-works and the conan install reference linked in the issue. Compare how revisions are represented with conan install and document valid usage, including the relationship to lockfiles. Done means the install section clearly explains supported revision cases and includes a correct example.

Written by the indexing model from the issue text.