Remove optional dependency `gflags`

Closes #59

See merge request zdvresearch_bsc/adafs!109

`gflags` is an optional dependency of RocksDB, it is used only for cli
tools that we don't use.

Update mercury to V1.0.0

See merge request zdvresearch_bsc/adafs!108

Cleanup RPCs

See merge request zdvresearch_bsc/adafs!104

Since now there is only one margo instance there is no more difference
between RPC and IPC.

All the "ipc" occurence in the code have been removed in favor of "rpc"

removed `MARGO_FORWARD_TIMER` option that allows to measure RPCs timing

Fix host lookup

See merge request zdvresearch_bsc/adafs!107

introduced `get_uri_from_hostname` function

Lookup of the local daemon is not different from a remote one thus we
can use the same code.

remove boost algorithm dependency

See merge request zdvresearch_bsc/adafs!105

Added Log to Readme and allow alphabetic LOG_LEVEL

See merge request zdvresearch_bsc/adafs!103

update mercury dependency

See merge request zdvresearch_bsc/adafs!102

update argobots dependency

See merge request zdvresearch_bsc/adafs!101

As discussed here:
https://xgitlab.cels.anl.gov/sds/margo/issues/43

There is no more need to clone the fork repository of argobots. We could
directly use the original one because all the patches required for margo
have been merged upstream.

bugfix: rmdir must not remove regular file

See merge request zdvresearch_bsc/adafs!99