beremiz

make attribute CFLAGS and LDFLAGS optional and add default empty value

Actually CFLAGS and LDFLAGS are not required and can be empty.
Without default empty value if target platform in project settings was
set to "Linux" CFLAGS and LDFLAGS was initialized with NoneType.
The result was broken build and it wasn't to save/load project with
such settings.

Traceback (most recent call last):
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 956, in _Build
if not builder.build() :
File "/home/developer/WorkData/PLC/beremiz/beremiz/targets/toolchain_gcc.py", line 96, in build
Builder_CFLAGS = ' '.join(self.getBuilderCFLAGS())
TypeError: sequence item 0: expected string, NoneType found
Beremiz installation
====================
Windows
-------
Download installer, install.
Linux
-----
Pre-requisites::
# Ubuntu/Debian :
sudo apt-get install python-wxgtk2.8 pyro mercurial
sudo apt-get install build-essential bison flex python-numpy python-nevow
Prepare::
mkdir ~/Beremiz
cd ~/Beremiz
Get Source Code::
cd ~/Beremiz
hg clone http://dev.automforge.net/beremiz
hg clone http://dev.automforge.net/plcopeneditor
hg clone http://dev.automforge.net/matiec
Build MatIEC compiler::
cd ~/Beremiz/matiec
./configure
make
Build CanFestival (optional)::
# Only needed for CANopen support. Please read CanFestival
# manual to choose CAN interface other than 'virtual'::
cd ~/Beremiz
hg clone http://dev.automforge.net/CanFestival-3
cd ~/Beremiz/CanFestival-3
./configure --can=virtual
make
Launch Beremiz::
cd ~/Beremiz/beremiz
python Beremiz.py