Add functionality to open a new tab to a specified directory via dbus

[bsteinfeld]

Modified the dbus add_tab function to accept a string parameter

denoting the initial directory of said new tab. This change is partially hacked (I originally made these changes on an old version of guake which had different parameters for the "add_tab" function. Thus when I migrated my code to V4.0 I simply used a instance variable to pass the data), but seems to be working!

This is a useful change because it allows the enduser to open a new tab on a specific folder via dbus. For example, one now has the ability to add an action in Nautilus which opens a new tab in Nautilus' current directory (like similar functionality for gnome terminal).

[bsteinfeld]

The patch file formatted by git-format-patch

[lincoln]

Hi bsteinfeld,

Thank you very much for your contribution. Based on your idea/implementation I've done it. I'll try to do something about nautilus actions to comment on bug #126. Thank you!