Add support for mknod,rmnod hook functions

This commit only supports TCP clients and servers partially
Add supports for DNS and packet socket services
Change mount point to /net and allow others to access
packet_socket_op: throw an exception with invalid ifname
dns_example: get hostname from the command line
tcp_server_example: remove node before return
move make_unique_ptr() to planet/utils.hpp
fix mount point of an example and add comments to planet_operation
Merge branch 'namespace_mod'

Add supports for mknod and rmmod hooks
Now file operations can share their data through the file_entry