Check width of a character

Add a restriction for a character option mentioned in TODO in
commit 23be268. It must be represented on one column.
Initialize struct gol to zero

Valgrind complains about ncurses_alive_character and
ncurses_not_alive_character not being initilized:

 ==16639== Conditional jump or move depends on uninitialised value(s)
 ==16639==  Uninitialised value was created by a heap allocation

Fix this by initializing struct gol to zero.
Use bit flags to know which options are set
Add file option

Add an option to read game's starting position from a file.