This PR moves the introduction about the different installation methods and editions found on the
install/install.rst page directly under the main install/ page. It creates three pages, one per
installation method documented on the install/install.rst page (Docker being documented on
docker.com and maintained by us), and moves the related content there. In addition, it fixes various
typos/grammar issues and improves the content according to the documentation guidelines. Various
references and links across the documentation had to be fixed accordingly.
task-3459070
closesodoo/documentation#5493
Signed-off-by: Xavier Platteau (xpl) <xpl@odoo.com>
