This change includes:
1. Move shared library `shadowsocks-libev.so.*` to an package `libshadowsocks-libev`
and rename package `shadowsocks-libev-devel` to `libshadowsocks-libev-devel`
to reconcile with the deb packages.
2. Add a new package `shadowsocks-libev-zsh-completion`.
3. Run `setcap` after installation (similar to #1119).
4. Remove ss-nat because it is designed for OpenWrt/LEDE.
5. Auto restart instantiated services after update and stop/disable instantiated
services after uninstallation.
As discussed with @librehat in #1604, maintaining a separate set of systemd
files for RPM distributions will be convenient to build on Copr.
This patch will also change some lines in rpm/genrpm.sh to archive the
source code using `git archive` because the old logic doesn't respect
`.gitignore`.
Yuxiang Zhu