opendir need to check that the given path is actually a directory
before to open it.

Moreover now open can be called with the O_DIRECTORY flag in order to
open an existent directory

The `cp` command double check the inode number to detect file changes
during transfers, we need to set it properly and keep it consistent.

inode(file) = std::hash(file_path)

In the daemon read handler manage read beyond end of file as normal case
and not exceptional

According to the read manpage a read could return less bytes then
requested due to an interrupt or an error.

We now try to repeat the read operation until all the existent data have
been read correctly.

It is possible that we read less bytes then requested cause the actual
file doesn't have so much.

The ChunkStorage class now store the chunksize in order to perform
runtime checks upon chunks bundaries.

Mercury now support shared memory autorouting.

A single margo instance can be initialized and it will handle both
shared memory communication and remote ones.

If the endpoint of the RPC is local mercury will automatically use
shared memory.

Since there is only one margo instance all the duplicated code for
rpc/ipc have been unified and simplified considerably.

------

The way in which client contact the server has changed.

 - Server initializes its own margo instance and generate the endpoint
communication string using `HG_Addr_self`.
 - This endpoint description string is written on the pid file
 - When the client library loads it will fetch the server endpoint
description from the pid file and will use that to contact the server.

I couldn't figure out why this is happening, but the inline function
cannot be found at runtime

ensure rpc_addresses object have been initialized before we use it for
the first time

margo, argobots and mercury have been updated. The abt-snoozer dep
required by margo it is not needed anymore.

RocksDB has been also updated to the lastest release

loggers can be now configured at execution time, by using environment
variables for both server and client.

Server:
 - ADAFS_LOG_LEVEL
 - ADAFS_DAEMON_LOG_PATH

Client:
 - ADAFS_LOG_LEVEL
 - ADAFS_PRELOAD_LOG_PATH

Since we introduced the `initialized` flag in the preload context, it is
not needed anymore to check for ld_is_aux_loaded flag.
In fact ld_is_aux_loaded is true if and only if the `initialized` flag
is true.

The library intercepts IO functions from others library constructors
before our constructor have been executed.

All the interceptions triggered before that our constructor have been
executed are now forwarded to the glibc.

By moving the logger initialization outside of the passthrough
initialization we will be able to implements fopen interceptions.

Avoid the usage of a custom cmake "find-module" for mercury.
Instead use the official exported target

In the glibc both readdir and closedir functions marks the @dirp parameter
with a non-null attribute.
If we use a compiler optimization level grater then 1,
the `dirp == nullptr` expression is evaluated to false
at compilation time and the relative if blocks is cutted out
of the final binary.

In order to avoid this bheaviour, we implement a functions and then set
that as weak alias of the real glibc function call.

readdir and closedir in glibc returns a EINVAL if the directory pointer
passed as parameter is NULL