Updated documentation.

README

src/lib-sieve/ext-encoded-character.c

src/lib-sieve/ext-envelope.c

src/lib-sieve/ext-fileinto.c

src/lib-sieve/ext-reject.c

src/lib-sieve/plugins/imapflags/ext-imapflags.c

src/lib-sieve/plugins/include/ext-include.c

src/lib-sieve/plugins/variables/ext-variables.c