Fix localstatedir to be /var/lib/opendnssec

Currently the localstatedir (which contains the subdirectories signconf, signed, unsigned, tmp) is defined as /var/opendnssec. This is in violation of the Filesystem Hierarchy Standard:

"Applications must generally not add directories to the top level of /var. Such directories should only be added if they have some system-wide implication, and in consultation with the FHS mailing list."
– http://www.pathname.com/fhs/pub/fhs-2.3.html#THEVARHIERARCHY

The proper place is /var/lib/opendnssec. The attached patch fixes this.

The patch also replaces all occurrences of the hardcoded path "$(localstatedir)/opendnssec" with "@OPENDNSSEC_LOCALSTATE_DIR@" (as defined in m4/opendnssec_common.m4).

Likewise, it replaces all occurrences of paths with hardcoded "@sysconfdir", "$(datadir)" or "@datadir@" to use their proper counterparts like "@OPENDNSSEC_SYSCONF_DIR@" or "@OPENDNSSEC_DATA_DIR@". A superfluous definition of "signerdir" in signer/src/Makefile.am is removed.

A hardcoded path in conf/conf.rnc and conf/conf.rng is also fixed, but the macro "@OPENDNSSEC_LOCALSTATE_DIR@" will not be expanded as the file is currently not handled by autoconf. The path just appears in a comment so I don't believe it's a big deal. The same applies for enforcer/utils/convert_database.pl which contains a hardcoded path in the documentation. The patch fixes this as well.

The patch applies cleanly to OpenDNSSEC 1.4.0a3.