margo context id is not the id of the host that send the request. Is the
internal context id of local margo instance.

Implement proper error propagation and handling on get_dirents RPC.
Error happening on the deamon are now embedded on the returned response
and the client throws an exception once he receives the response.

Shared-memory communication can be disabled through cmake
compile time option `-DUSE_SHM:BOOL=OFF`

Refactored initialization code.

 - More detailed logging
 - Use exceptions to better propagate errors
 - Log signal type before shutdown

Daemon is now capable of providing version information through the
`--version` cli option.

Get rid of all the occurrences of old project name "adafs" from output
strings and documentation

`adafs_daemon` -> `gkfs_daemon`

get rid of adafs name from folder names

A new cli parameter `--listen`,`-l` allow to specify binding address/interface

RPC port can now be configured at runtime through `--bind-port` command line argument.

For some comunication layers an out of band communication is required for putting in place the specific protocol handshake.

In those case a shared lookup file could be used to distribute deamon's endpoints information to all the clients.

This file need to resides on a shared filesystem and can be specified using the new CLI parameter `--lookup-file`.

When the pid file already exists don't try to kill the previously
running daemon. Just print an error and exit.

gid and uid metadata fields have never been used and can be removed
safely

The access RPC have been removed. The POSIX access functionality now is implemented through the stat RPC. This makes code easier to maintain and modify.

There would be a little performance degradation on the POSIX access
function because we are now retrieving also the metadata
associated to the file.

This change makes a lot easier to add symlink support