Enotify: finished skeleton by addin empty :encodeurl implementation.

src/lib-sieve/plugins/enotify/Makefile.am

src/lib-sieve/plugins/enotify/ext-enotify-common.h

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

src/lib-sieve/plugins/enotify/vmodf-encodeurl.c

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

src/lib-sieve/plugins/variables/ext-variables-common.h

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

src/lib-sieve/plugins/variables/ext-variables-modifiers.h

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

tests/extensions/enotify/execute.svtest