feat/bus installer api

[JarbasAl]

similar to skills https://github.com/OpenVoiceOS/ovos-core/blob/dev/ovos_core/skill_installer.py

a bus api should be introduced to install plugins

https://github.com/OpenVoiceOS/ovos-audio-transformer-plugin-ggwave should also be updated to decode PPLUG:{pypi_name} and allow installing plugins by audio

a "appstore" for plugins can then be made similarly to https://github.com/OpenVoiceOS/OVOS-skills-store