[db/avltree] drop unused header - <boost/utility.hpp>
[db/avltree] implement del() command.
[db/avltree] set() command: firstly check maybe such key already exist.

Before this patch there will be duplicates in Db::AvlTree::m_nodes
(std::list), while we just need to change value on already existed item.
[db] add TODO about bulk set/get/del commands
[kernel] numberOfArguments paramater for commands callback.

Before this patch every callback must check number of arguments itself,
this patch implement common check for number of arguments for commands
callback.
[kernel/commands] make struct CallbackInfo, HashTable typedef private.

There is no need to public this.
[db] hide some typedefs (HashTable::Table, Inteface::{Key,Value})
[kernel/net] stop server by signals (SIGINT, SIGINT, SIGINT)
[utils] simple boostcache client in CLI.

- rlwrap to add readline support
- rlwrap to add autocompletion