v3.0.0: Major changes with POSIX support.

New features

• lib/opkg: Add support for OpenWrt (and alike)
• Bash is not required on Alpine, SunOS or OpenWrt:
  The program can work perfectly with POSIX shell on those systems.
• Single script can now execute within POSIX or non-POSIX
  environment and it detects/loads features dynamically.
  If the system has bash installed, the program switches to
  bash as soon as possible.

Fixes and Updates

• tests/: Support new ubuntu/debian systems
• lib/yum, lib/dpkg, lib/apk: Fix #96, #143
  by adding -q (quiet) option for Qs.
• lib/00_core.sh: POSIX going well
• lib/zz_main.sh: POSIX going well
• lib/apk:
  • Fix many implementation issues.
  • Q prints version information.
  • Fix --noconfirm issue (#150)
  • POSIX version (pacapt-POSIX works perfectly without bash)
• Remove {apk,dnf,zypper}_Sw methods
  and fix the --download-only for them