Spawn open task

[jawira]

Hello, I modified OpenTask a little bit:

• Everything works as expected when I open an url. But when I open a file, for example an image, the program blocks the terminal until the program is closed. That's why I added "spawn=true" option.
• I added "passthru=false" to hide any message in console.

[mrook]

I clicked merge too fast. This PR breaks the third test case in OpenTaskTest. Can you take a look at that @jawira ?

[jawira]

@mrook my fault, I will check that tonight.