Bug fixes and cleanup

add after syntax file
return to 16 highlight level as most colour schema are made for multiples of 4.
Option to add all commands
update quick installation

merge @jwilkins improvements.

@jwilkins colour scheme without terminal background colour

merge @charlietanksley improvements

colour scheme without background colour from @charlietanksley

merge @autre improvements

Improvements and colour scheme from @autre

merge @slve improvements.

Improvements and colour scheme from @slve