Connect basic Controller functions to menu bar actions

[AntonJuliusRabe]

methods handling menu bar actions are defined in MenuController and ready to be connected to basic methods like open, save and validate. Just for us to have something we can show It set handleOpen to call open from the imported controller package for now.

[zakharc]

@JuliWanner read() method returns null all the time. I've made a quick fix for it c186df4. Could you please take a look?