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.

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.

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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.

margo, argobots and mercury have been updated. The abt-snoozer dep
required by margo it is not needed anymore.

RocksDB has been also updated to the lastest release

Instead of using custom variable to search for installed libraries
we can rely on the standard `CMAKE_PREFIX_PATH` [1]

[1]: https://cmake.org/cmake/help/v3.8/variable/CMAKE_PREFIX_PATH.html#variable:CMAKE_PREFIX_PATH

Avoid the usage of a custom cmake "find-module" for mercury.
Instead use the official exported target

gflags is needed to compile rocksDB but not to link with it

CMAKE_CXX_FLAGS_RELEASE already defines "-DNDEBUG" and "-O3".
We set them just to be sure that even in older/newer version of Cmake
they are set correctly

When rocksdb is build with jemalloc linking with adafs was failing