Support for the following calls has been added:
 - opendir
 - readdir
 - closedir

The readdir call use the new RPC get_dirents that ask to all the
nodes (broadcast) about all the existing first-level entries
of a specific directory.

In order to support directories functionalities
opendir,readdir,closedir,etc.. the OpenDir class has been introduced.
This is a new specialization of the OpenFile class so that OpenDir
object can be stored in the open_file_map along with regular file.

Allow to add already instantiated OpenFile to the OpenFileMap.

This will come in hands when we will have sub-classes of the OpenFile.
In that case this new add function will accept all object that are
derived from the OpenFile class. See directories functionalities.

In the case the open call has been called with the O_DIRECTORY flag the
ENOTSUP (Operation not supported) will be returned.

Paths are now made relative to the mountdir at client side.

The new relativize_path fucntion in the PreloadContext is used to check
if a path is relative to the pseudo-mount directory and to make it
relative

The new PreloadContext class is used as singleton to store the general context
information of the interception library.

The plan is to move global accessed variables into this sigleton.

At the moment just the logger object has been moved into it.

In case the glibc could not be loaded through dlopen print the relative
error and exit from the client

It is only relevant for sparse files but the current implementation
has a too high overhead on a single node (~10%). We need to find
a better solution at a later point.

This is an optimization for mdtest which shows very slow performance
in removing files, getting worse with an increasing number of nodes.

Postpone the creation of the OpenFile object until we are sure that the
file actually exists and we have enough access rigths for it.

Problem:
In the case the path for which the check access is performed doesn't
exists the server will set `out.err` with the correct error number (ENOENT).
On client side the value of out.err is used as return value but the
errno variable is not set.

Assert is put after a more detailed error message is written to the log.

Previously, host rpc addresses have been looked up lazily when a request
was done. This is not necessary as all hosts are looked up anyways
while the file system is running.

Now, all RPC addresses are looked up when the environment is initialized.
After that, the rpc_address map is only accessed read-only and does not
require a mutex anymore.

Since POSIX.1-2001 the S_IFMT (0170000) bitmask of the file mode must
contain the file type.

At the moment we correctly support
 - [S_IFREG] regular file
 - [S_IFDIR] directory

Previously, clients would look for the daemon by name which was not robust.
If the daemon was started with valgrind for example, clients would not find
the daemon.

Similar to other applications a daemon now creates a pid file with
information about its pid and its started mountdir.

Proper errorhandling on server and client side was added.

Multiple daemons per node are explicitly not allowed for now!

target was the index of the cycle and target[target] was the actual
identifier of the target. In some part of the code target was considered
as the identifier directly.

Now the index of the cycle is i and target is the actual identifier of
the target.

The calculus (on clients) about the last chunk involved into a
write/read operation was bugged.

A new blocks_calc_util library has been introduced in order to make
easier to perform this kind of calculus.