Screenshot: added File Save dialog.

Also refactored a bit the delay thingy -- now vera doesn't block when waiting
for the delay to elapse.
Screenshot: do not take the screenshot directly from the Gdk.Window, but use instead a region from the entire root window.

This makes sure that we correctly get (by playing with the with the width/height) the window borders.
As a bonus, transparency is not fucked up anymore.
Screenshot: added screenshot via selection support.

This is still at its early stages and has room for improvement but so far, so good.
ScreenshotSelectionWindow: assume the user aborted if the selection_width or selection_height are 0.
ScreenshotSelectionWindow: handle cases when end < start
ScreenshotSelectionWindow: display the black mask even when the selection has not been started.
ScreenshotSelectionWindow: use vera-color if available for the mask color.
ScreenshotSelectionWindow: bugfix for selection_source.
Added screenshot selection support in vera-command.
Screenshot: remember the last directory where a screenshot has been saved.

This is accomplished using the new last-screenshot-directory key in the
org.semplicelinux.vera schema.
Screenshot: added ScreenshotTakeDialog, an interactive frontend for vera's screenshot capabilities.

Use the DBus method Interactive() or vera-command to invoke it.
There is also a convenience .desktop file that ships in /usr/share/applications and that does the same thing.

In a separate note, we are at 0.35!
libvera.so is not meant to be here.
Merge branch 'master' into debian
debian/vera-desktop.install: ship /usr/share/applications.
0.35-1