Highlight program name in code examples

Fixes more than one command name per variable highlighting bug
Should be easier to read and understand
Fix example_variable_style typo

Remove config option short versions
Indent README code examples over using code blocks
Rename colour to color to stay consitent with rust
Remove Ord derives
raw_style.into() over Style::from(raw_style)
Remove impl From<IoError> from TealdeerError
Add debug print to command name lookup
Write errors to stderr whenever exiting with non zero return code
Rename Config::new() to Config::load()

Add example to inkscape input with multiple command occurrence

Else indentation
Serde rename
Generalize config, rename and make style member

This feature was deemed potentially too confusing

dispay-config might be misleading, as this option does not display the 
config content

Make it a bit more colorful, like the previous style

This allows the user to omit the fields when creating a config file.