Build by default with optimization level -O2 for GCC

before -O0 was used by default, that caused pretty bad performance.

Amd64, i6700k, 4200MHz, GNU/Linux (non-RT kernel), gcc 7.2.0

-------------------------------------
Optimization | EN/ENO |no EN/ENO |
-------------------------------------
default | 11 | 9.5 |
-O3 | 3.9 | 5.2 |
-O2 | 4 | 4.8 |
-Os | 4.1 | 3.5 |
-Ofast | 3.9 | 5.2 |
-------------------------------------

ARM, BBB Cortex-A8, 600Mhz, GNU/Linux, gcc 4.6.3

-------------------------------------
Optimization | EN/ENO |no EN/ENO |
-------------------------------------
default | 273 | 226 |
-O3 | 141.8 | 106.2 |
-O2 | 142 | 107 |
-Os | 152.5 | 112.2 |
-Ofast | 141.7 | 106.2 |
-------------------------------------

For embedded systems with size constaints (like Cortex-Mx, AVR and so
on) I usually use -Os. It gets pretty good results. For
GNU/Linux-based systems -O2 is usually a good choice, as you see the
test results.

Crossbar test router configuration is available in .crossbar directory.

Starting command:
crossbar start

This project contains wamp client config to be loaded at runtime startup.

project_files/wampconf.json

wampconf.json is in "Project Files", so it is copied to runtime's working directory, and then loaded after program transfer + runtime restart.

Otherwise, wamp config file path can be forced :
./Beremiz_service.py -c /path/to/my/wampconf.json /working/dir

Otherwise, path for CRA secret can be forced :
./Beremiz_service.py -s /path/to/my/secret /working/dir

Tested on version:
 Crossbar.io        : 17.12.1 (Crossbar.io COMMUNITY)
   Autobahn         : 17.10.1 (with JSON, MessagePack, CBOR, UBJSON)
   Twisted          : 17.9.0-EPollReactor
   LMDB             : 0.93/lmdb-0.9.18
   Python           : 2.7.12/CPython