Reformatted code w.r.t. unifying code styles as of the official
CPPCoreGuidelines by Stroustrup and Sutter

Restructuring code w.r.t. configurations and definitions:
- #defines have been mostly removed from configurations
- a dedicated config file has been added for configurations with constexpr
- past configure file is now only a cmake wrapper
- wrapping global functions into namespaces

Removed all adafs and ifs occurrences. Now called gkfs

CREATE_CHECK_PARENTS controls if the existance of the parent node needs
to be checked during the creation of a child node.

Example: The check prevents the creation of file `/parent/child`
if `/parent` doesn't exists or if it is not a directory

By default CREATE_CHECK_PARENTS is enable and the check is enforced.
It can be disable to speedup creation operations by passing
`-DCREATE_CHECK_PARENTS:BOOL=OFF` as cmake parameter.

The new `LOG_SYSCALLS` Cmake flag can be used to enable verbose logging of
system calls interception.

We don't want the log file to be created before command line parsing,
otherwise --version or --help cli option could not work beacause we
don't have permission to write to log file.

Write errors happenig on deamons are now reported back to clients.
"No space left on device" error is now properly propagated to clients.

Port is only meaningful for some of the communication protocols. For
instance psm2 is not using it at all.

Port can be still specified using the --listen,-l flag:

Example:
```
gkfs_daemon --listen "localhost:1234"
```

margo context id is not the id of the host that send the request. Is the
internal context id of local margo instance.

Implement proper error propagation and handling on get_dirents RPC.
Error happening on the deamon are now embedded on the returned response
and the client throws an exception once he receives the response.

Shared-memory communication can be disabled through cmake
compile time option `-DUSE_SHM:BOOL=OFF`

Refactored initialization code.

 - More detailed logging
 - Use exceptions to better propagate errors
 - Log signal type before shutdown

Daemon is now capable of providing version information through the
`--version` cli option.

Get rid of all the occurrences of old project name "adafs" from output
strings and documentation

`adafs_daemon` -> `gkfs_daemon`