added setPlayerName()
reintroduced the player name text field
added getPlayerName() to Menu

returns the string in the text field
added getPlayerName() to Tower Defense

returns getPlayerName() of the menu
Level selection gets created when player clicks StartGame
starting game sets the player name to the value in the text field
better gui positions
cleanup
added setName() to Player
player name now displayed ingame
better cursor position in player name text field
aligned tower buttons to new gui
Merge branch 'feature/issue/#20' into develop