Add `bump` command

[pereorga]

The bump command would increase the lower limit of the phar tools to the currently installed versions.

For example, see composer bump command: https://getcomposer.org/doc/03-cli.md#bump

[pereorga]

FWIW, this is what I'm doing in bash (GNU/BSD sed/grep):

##############################################################################
# Updates phive, installs newest versions of PHIVE packages, and bumps versions.
# Arguments:
#   None
##############################################################################
update_phive() {
    yes | php -d memory_limit=256M tools/phive selfupdate
    yes | php -d memory_limit=256M tools/phive update --force-accept-unsigned

    # Bump versions
    local -r xml_file=".phive/phars.xml"
    while read -r line; do
        if [[ "${line}" =~ ^[[:space:]]*\<phar ]]; then
            local name version installed updated_line
            name=$(echo "${line}" | sed -E 's/.*name="([^"]+)".*/\1/')
            version=$(echo "${line}" | sed -E 's/.*version="([^"]+)".*/\1/')
            installed=$(echo "${line}" | sed -E 's/.*installed="([^"]+)".*/\1/')

            updated_line=$(echo "${line}" | sed "s/version=\"${version}\"/version=\"^${installed}\"/")

            if [[ "${line}" != "${updated_line}" ]]; then
                sed -i'.original' -e "s|${line}|${updated_line}|" "${xml_file}"
                rm "${xml_file}.original"
                echo "Updated ${name}: ${version} -> ${installed}"
            fi
        fi
    done < "${xml_file}"
}

It is not exactly the same as the composer bump command, this just copies the installed version to the required version.