Replace all occurrences of [ with [[ in bash and zsh scripts and
configs.
Performance wise it makes sense to use the builtin instead of calling an
external command also when from a functionality stand point `test` would
suffice.
Keep output of git "live" (Meaning that one can see live what submodule
is currently pulled) by not saving it first and then grepping but by
catching a failing grep when the output of git was empty.
Move long commands from the dotbot config into own scripts to keep the
install.conf.yaml more readable.
Fix bug that the submodule init step fails when already done once since
then the grep statement fails because there is no output.
