Merged sieve-exec tool into sieve-test.

doc/man/sieve-test.1

doc/man/sievec.1

doc/man/sieved.1

src/lib-sieve/cmd-discard.c

src/lib-sieve/sieve-result.c

src/lib-sieve/sieve-result.h

src/lib-sieve/sieve.c

src/sieve-tools/Makefile.am

src/sieve-tools/sieve-exec.c

src/sieve-tools/sieve-test.c