Fails silently when target directory is write protected

[balazsdukai]

In case the target directory for the output is not writable, 3dfier completes the process without any warnings or errors, but it doesn't write any output. This is quite tricky, since it give the user the idea that 3dfier succeeded.

[vvmruder]

I would add the idea of checking correct permissions in the begin of the process. To not let the user wait until the end to know it was not possible to write the data.

[tcommandeur]

There are checks to see if a folder and file has write access in the main.cpp file. Cross platform permissions checks are rather difficult to implement.