Review and fixes that died when rebasing all commits

Nafi3 authored Mar 12, 2018 and Marc Vef committed Mar 23, 2018

This commit gives new options regarding separation of metadir and rootdir location. If only rootdir destination is given both metadata and data is stored at the same path

- 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.

ADA-FS's statfs will fill the struct mostly with rough estimations.
It is not supposed to return accurate data but "some" data for applications to work

Preload lib: RPC/IPC Mercury/Margo environments are only initialized if the mountdir path is used by the application
For that, the daemon writes the mountdir (it was started with) to a configurable path to disk.
The libraries read this value and only the process that uses part of this path will actually trigger the environment initialization.
This forbids prior behavior where applications initialize the whole environment numerous times, although unused.
For example, any MPI program will spawn multiple processes, all with the LD_PRELOAD environment variable set.

Added: register daemon to system for storing auxiliary files + better daemon startup and shutdown handling

- 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"