fixed way to find available platforms

Since OpenCL provides a way to find the number of available platforms,
the command dispatcher now uses it.
fixed bug in ctor of option (unitialized member)
changed naming in square_matrix

naming of rows and columns was inverted
Merge branch 'unstable' of github.com:Neverlord/libcppa into unstable

Conflicts:
	src/opencl/command_dispatcher.cpp
Merge branch 'unstable' of github.com:Neverlord/libcppa into unstable