Clean up SPEC file template

Use `%global` definition for Shellfu requires and cluster fields
according to relevancy (source vs. build).

packaging/template.spec

-Name:           __MKIT_PROJ_PKGNAME__
-Version:        __MKIT_PROJ_VERSION__
-Release:        1%{?dist}
-Summary:        __MKIT_PROJ_NAME__ - __MKIT_PROJ_TAGLINE__
-URL:            __MKIT_PROJ_VCS_BROWSER__
-License:        GPLv2
-Source0:        %{name}-%{version}.tar.gz
-BuildArch:      noarch
-
-Requires:       imapfilter
-Requires:       shellfu >= 0.10, shellfu < 0.11
-Requires:       shellfu-bash-pretty
-
+%global shellfu_req shellfu >= 0.10.4, shellfu < 0.11
+
+Name:       __MKIT_PROJ_PKGNAME__
+Version:    __MKIT_PROJ_VERSION__
+Release:    1%{?dist}
+Summary:    __MKIT_PROJ_NAME__ - __MKIT_PROJ_TAGLINE__
+URL:        __MKIT_PROJ_VCS_BROWSER__
+License:    GPLv2
+Source0:    %{name}-%{version}.tar.gz
+BuildArch:  noarch
+
+Requires: %shellfu_req
+Requires: imapfilter
+Requires: shellfu-bash-pretty
 %description
 imapdomo is simple convenience wrapper around imapfilter that
 adds few more Lua functions and suggests some system to way how you can