Changes:
- transitional_highlight isn't created when both retrieval of fg or bg
has failed
- Transitional highlight is not looked for when section separators are
disabled
- empty section no longer returns highlight group as section data
* Enhance Theme
- loaded theme table is nolonger stored in configs and thus not passed
to components. Insted it's cached in highlights.lua
- Reintroducing clear_highlights turns out themes can still change if
setup is called more than once
* Add error messege for invalid theme
It stops lualine from crashing in such incedent
* Apply lua-format
* Small tweeks
Hubert Pelczarski
Shadman
hoob3rt