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

This commit updates Hermes to v0.4.1 and configures it to generate RPCs
with "instrumentation breadcrumbs" that can be understood by servers
relying on Margo >= v0.5.2. Fixes #72.

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.

Fixes an issue where client applications such as ssh might attempt to
close all open fds, therefore also closing the fds used by the internal
components of the library such as Mercury.

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

CCI plugin have been tagged as deprecated in the Mercury library. We
where using it just for verbs, OFI+verbs can be used now as replecement.

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

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

change CMake project name `ifs` -> `GekkoFS`

Don't use custom format for the build type log entry.

Fix typo

Metadata class needs to be used by both the client and the daemon

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.

Searching for mercury dependencies is useless. In fact if a library has not been linked and enabled while mercury was built, we won't be able to use it.

Moreover, mercury ships with a make module that provides which links flags needs to be used. Thus there is no need to search for mercury dependencies.