renamed problem directories
added php p8 solution
added php p9 solution
refined p9 php solution
added php p010 solution
added p010 c sieve solution
updated p10 c sieve to use 0 instead of -1
added p10 php sieve solution
optimized p10 php sieve
half memory optimized sieve php p10
optimized memory sieve p10 c
added php p011 solution