initial commit for invoice ninja
added invoice ninja submodule
add docker ignore
removed tests folder
added possibility to define environment variables
Merge commit '406dc0c0110dbccc390d46c042f10cb6224bb692'

* commit '406dc0c0110dbccc390d46c042f10cb6224bb692':
  Initial commit

added read me for invoice ninja build
create a lock file to only run database migrate once