Compile UI file into tilda binary
Update po/ directory
Option to hide tab bar and border while multiple tabs are open

 * Added an extra option "Hidden" to "Position of Tabs"
 * Effect will apply on option selection, opening new tab and on launch
 * This should also solve issue #81

Signed-off-by: Sebastian Geiger <sbastig@gmx.net>
Preferences: Fix label being cut off
Update po/ directory