luci-ssl-openssl: use OpenSSL for key generation, drop px5g
luci-ssl-openssl: use OpenSSL for key generation, drop px5g

Replace a dependency for px5g with openssl-util. Both LEDE and
Openwrt have now uhttpd versions that can generate keys with
OpenSSL cmd tools if px5g is not found. This change enables an
"OpenSSL-only" version of LuCI without mbedTLS/PolarSSL.

(Note: if px5g is found, uhttpd will prefer that.)

Relevant commits in uhttpd:

LEDE:
https://github.com/lede-project/source/commit/3c4858eeb2bbb3107f87bb3be07d5c172c8e0ef9
https://github.com/lede-project/source/commit/82132540a3efbc98f8f4379b26d4b4541013e69d
https://github.com/lede-project/source/commit/9097dc5ad844c336020be11085e1c8c80390ac9c

Openwrt:
https://github.com/openwrt/openwrt/commit/6ec32832d25335355d205c4601d4a8ca5dfd6808

Signed-off-by: Hannu Nyman <ab53a3387de93e31696058c104e6f769cd83fd1b@iki.fi>

openwrt-es/openwrt-luci,Wedmer/luci,wongsyrone/luci-1,openwrt/luci,tobiaswaldvogel/luci,981213/luci-1,taiha/luci,nmav/luci,kuoruan/lede-luci,lbthomsen/openwrt-luci,lbthomsen/openwrt-luci,taiha/luci,Wedmer/luci,aa65535/luci,tobiaswaldvogel/luci,nmav/luci,hnyman/luci,remakeelectric/luci,openwrt-es/openwrt-luci,chris5560/openwrt-luci,kuoruan/lede-luci,taiha/luci,kuoruan/luci,oneru/luci,lbthomsen/openwrt-luci,wongsyrone/luci-1,chris5560/openwrt-luci,oneru/luci,981213/luci-1,lbthomsen/openwrt-luci,chris5560/openwrt-luci,LuttyYang/luci,LuttyYang/luci,hnyman/luci,hnyman/luci,wongsyrone/luci-1,Wedmer/luci,wongsyrone/luci-1,openwrt-es/openwrt-luci,shangjiyu/luci-with-extra,LuttyYang/luci,openwrt-es/openwrt-luci,Wedmer/luci,remakeelectric/luci,taiha/luci,wongsyrone/luci-1,shangjiyu/luci-with-extra,openwrt/luci,wongsyrone/luci-1,rogerpueyo/luci,shangjiyu/luci-with-extra,artynet/luci,lbthomsen/openwrt-luci,oneru/luci,Noltari/luci,LuttyYang/luci,tobiaswaldvogel/luci,Noltari/luci,Noltari/luci,openwrt/luci,taiha/luci,chris5560/openwrt-luci,chris5560/openwrt-luci,shangjiyu/luci-with-extra,aa65535/luci,shangjiyu/luci-with-extra,aa65535/luci,981213/luci-1,981213/luci-1,aa65535/luci,Noltari/luci,Noltari/luci,artynet/luci,shangjiyu/luci-with-extra,remakeelectric/luci,artynet/luci,oneru/luci,Noltari/luci,chris5560/openwrt-luci,openwrt/luci,kuoruan/lede-luci,LuttyYang/luci,aa65535/luci,openwrt/luci,Noltari/luci,LuttyYang/luci,openwrt/luci,nmav/luci,kuoruan/luci,taiha/luci,artynet/luci,aa65535/luci,taiha/luci,tobiaswaldvogel/luci,openwrt/luci,kuoruan/lede-luci,tobiaswaldvogel/luci,hnyman/luci,rogerpueyo/luci,rogerpueyo/luci,remakeelectric/luci,981213/luci-1,openwrt/luci,nmav/luci,artynet/luci,hnyman/luci,shangjiyu/luci-with-extra,kuoruan/luci,Wedmer/luci,rogerpueyo/luci,rogerpueyo/luci,rogerpueyo/luci,lbthomsen/openwrt-luci,openwrt-es/openwrt-luci,rogerpueyo/luci,LuttyYang/luci,kuoruan/luci,tobiaswaldvogel/luci,openwrt-es/openwrt-luci,kuoruan/lede-luci,hnyman/luci,981213/luci-1,chris5560/openwrt-luci,shangjiyu/luci-with-extra,wongsyrone/luci-1,tobiaswaldvogel/luci,artynet/luci,openwrt-es/openwrt-luci,Noltari/luci,hnyman/luci,Wedmer/luci,kuoruan/lede-luci,remakeelectric/luci,lbthomsen/openwrt-luci,nmav/luci,kuoruan/luci,wongsyrone/luci-1,openwrt-es/openwrt-luci,oneru/luci,nmav/luci,chris5560/openwrt-luci,lbthomsen/openwrt-luci,kuoruan/lede-luci,artynet/luci,remakeelectric/luci,981213/luci-1,oneru/luci,LuttyYang/luci,oneru/luci,nmav/luci,artynet/luci,aa65535/luci,aa65535/luci,nmav/luci,Wedmer/luci,remakeelectric/luci,kuoruan/luci,hnyman/luci,nmav/luci,remakeelectric/luci,Wedmer/luci,tobiaswaldvogel/luci,taiha/luci,artynet/luci,rogerpueyo/luci,kuoruan/lede-luci,Noltari/luci,kuoruan/luci,oneru/luci,kuoruan/luci