[FEATURE] Add support for UI customisation

[yadvr]

• Add supporton branding the UI: logos, and theme (refer: https://www.antdv.com/docs/vue/customize-theme/)
• Add user documentation on branding
• TBD - Introduce/use a config.js or config.json file for high level custom options (such as keyboards, configs etc.)

[yadvr]

@utchoang cc @svenvogel can you have a look at the issue of adding a theme for Primate. Ideally a json file that (1) Primate loads and applies, (2) the json/theme file does not get packed/bundled with rest of the code and is available say similar to index.html on the root dist directory. Same for any other branding logos/images.

[utchoang]

@rhtyd cc @svenvogel In primate, the logo is a component. But under this mission, I will change it to custom, right?

[yadvr]

I think what we can do is to move the logo (png and svgs) such that users can simply replace the files with their chose png/svg files after they use the dist/archive/deb/rpm used to install Primate

[yadvr]

Related legacy UI for tracking - apache/cloudstack#3258

[yadvr]

Got a PR