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.

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

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.

- Previously the directory hierarchy was not clear regarding to which
  file belong to which part of the project (client or daemon).
  Further, we will have other clients in the future (such as Fuse).
- CMake files now differentiate between include dirs for all targets
  and target specific ones.
- Removed duplicate -pg flag.
- Not listing header files when adding executables or libraries
  is considered bad practice. Note that include_directories() is adding
  include paths to the code while adding all files used for executables
  and libraries provide the context which files belong to each binary.
  When only include_directories() is set, CMake assumes that all files
  belong to a binary (which is not necessarily true). As a result,
  some IDEs may break as the do not support this assumption.

  In general we should almost always favor explicitness over implicitness.

- Add: adafs_access, open with check if object exists
- Add: root metadentry to database of each node
- Modified: Open, unlink, mkdir, rmdir and combined their functionality to "create node" and "remove node"