Support overrides

[siddhpant]

I want to use the emodipt-extend, but want to override some settings (like removing branch length limitation).

I can copy and modify, but that doesn't get updated.

Please allow overrides so one can have some modifications over default themes.

Related: #4189, #3078

[JanDeDobbeleer]

@siddhpant copy paste the theme and reference the location. Themes are only sample configurations.

[siddhpant]

The catalogue is too big to call it a sample though.

Plus, the samples get updated and can have bug fixes etc. when I update posh, so they aren't really treated as samples. A sample configuration in most projects is just one example file.

[JanDeDobbeleer]

@siddhpant but they are. Use then as they are, or copy and adjust to your liking.