[doxygen] fix INPUT_FILTER for TODO substitutions (.* -> [ @]*)
[db/interface] add defines for compiler __attribute__((unused))
[kernel] move toReplyString() into Command class.

There was Interface::valueToReplyString() before, but it shoudn't be in
Interface.
[kernel/commands] fix checking number of arguments for commands.

We need in greator-or-equal instead of just greator.
Because command can have zero arguments, and it means that command
didn't have any arguments.
For dynamic number of arguments use -1
[kernel/commands] add "COMMANDS" command, that print all available commands.

Will be used for autocompletion in futher
[utils/boostcache] use COMMANDS to fill words for autcompletion
[documentation] add commands to run server and CLI client into README.