changed cpus, disks, memory, processes custructors ; adjusted environment

Signed-off-by: Patrick Bäuerle <patrick.baeuerle@chinanetcloud.com>
added a link between the simulated file and a real file (to simulate content of a file) : added is_file() and get_file_content() to Disks class

Signed-off-by: Patrick Bäuerle <patrick.baeuerle@chinanetcloud.com>
solved merge conflicts