add method to check and clear rows in grid class
add checkAndClearRows to the UML
convert defines to using an enum for rows and columns
made destructor of level virtual
cast level to Level0 to read from the file
after a block is stopped, checkAndClearRows() and add points
rework the way score is calculated, also use helper methods for determining the command
add support for drop command
add code to move the grid down once rows about been cleared