Get the correct image src paths

[sockenklaus]

This commit checks whether the script is invoked via CLI or webbrowser and gets the correct image src path for both methods.

[tetsuo13]

Good catch! I haven't been able to do a lot of testing with image conversions.

I'd like to have more code reuse if possible. Instead of calling getLocalSettingsPath(), please change it so that $mwikiSettingsPath (declared on line 61) is passed in to convert() and then passed in to processImage(). This way the function is only called once during the start of the program.

[sockenklaus]

I defined a constant "MWIKI_ROOT" and used it during the img conversion. I think this is a little bit more elegant instead of passing aroung lots of arguments.

[tetsuo13]

Thank you.