added update method to clickable
gave Gameplay to clickables
buttons can now be unclicked, by clicking on them
added javadoc
fixed problems
started, so buttons will be set in Button class

added method currentTowerPlacable()
reversed changes in TowerButton
Tower now placed
now buttons unclick other buttons
cleanup
restructuring
if a button is unclicked you don't place a tower anymore
cleanup
adding new button system to GameComponent
added stayClicked to Clickables

if this variable it is true the clickable is supposed to not release,
when the mouse is released
now only clicked buttons are unclicked
now button not placeable sound is not played on button click
changed tower shadow alpha
Merge branch 'feature/cleaning' into develop