doc: fix another set of toctree warnings
    
    Convert some manual menus to toctree, put some more pages on
    toctree list; and on the pages where it doesn't make sense to hack
    on toctree integration use ':orphan:' to silence the warnings.
    
    /home/praiskup/rh/projects/copr/copr/doc/beaker_tests.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/building_package.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/contribute.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/copr_outdated_chroots_removal_policy.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/custom_source_method.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/git_guide.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/how_to_enable_repo.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/how_to_install.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/patch_process.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/screenshots_tutorial.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/src_rpm_upload.rst: WARNING: document isn't included in any toctree
    /home/praiskup/rh/projects/copr/copr/doc/webhook_hacking.rst: WARNING: document isn't included in any toctree