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.

exposes a new  DB function that allows to retrieve all the
first-level entries of a specific directory.

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

The path relativization code was not taking into a account corner cases
such as:
 - `/tmp/mountdir`
 - `/tmp/mountidr/`

Daemon: root directory must be relative

See merge request zdvresearch_bsc/adafs!69

Now that we use only relative path on daemon side,
also the initial creation of the root directory should be
use a relative path.

Daemon: introduce storage backend

See merge request zdvresearch_bsc/adafs!60

Acknowledge the main thread that the IO operation had terminate before
to actually close the file.

This is a "dirty" fix that waits to be refactored.

WARNING: Error on close will not be reported to the client that issued the IO
operation.

Data operation has been grouped under a ChunkStorage class
that will manage all the data backend operations.

The instance of this object is stored into the ADAFS_DATA sigleton.

Use CMake imported target for Boost components

See merge request zdvresearch_bsc/adafs!68

Introduce MetadataDB class

See merge request zdvresearch_bsc/adafs!67

Preload includes cleanup

See merge request zdvresearch_bsc/adafs!64

docker: changed dependencies build path

See merge request zdvresearch_bsc/adafs!66

The metadataDB class was using integer to return errors.
New exceptions classes has been introduced in order to be used as error
propagation method.

In this commit the MetadataDB::get function has been modified in order
to make use of exceptions.

move file map into context

See merge request zdvresearch_bsc/adafs!65

Multiple logs handling

See merge request zdvresearch_bsc/adafs!59

Use relative paths

See merge request zdvresearch_bsc/adafs!58

Signed-off-by: Marc Vef <vef@uni-mainz.de>

During daemon setup, multiple spdloggers are configured.

Using spdlog::get("<LOGNAME>") is possible to retrieve those and use
them in other part of the code.