Update "themeinfo" for Moodle 2.6 to use core_useragent.

Error message: "get_device_cfg_var_name" and "get_device_type_list" have been deprecated, please update your code to use core_useragent instead.

Copy the ThemeInfo command to the 2.6 commands, change the namespace "Moosh\Command\Moodle26\Theme" and implement the \core_useragent calls.