DF-1444. Landscape editors state is store between different scenes (tabs)
DF-1463. Added slider widget which allows to display the range and the value of the slider and change both from keyboard
DF-1529. Added ruler tool dock. Added slider to change ruler tool line width
DF-1745. String literals from landscape editors were moved to StringConstans.h file
DF-1747. Fixed Heightmap editor functionality. Added missing mode
DF-1753. Landscape editors docks was removed from View menu. Landscape editor docks are hidden until corresponding landscape editor is activated
DF-1777. Ruler tool point can be removed by pressing Backspace, one by one
DF-1778. Ruler tool preview is paused by pressing Esc. Unpausing by Backspace
Some other fixes