Make a lazy pearl init operation

[fsquillace]

Rather than initialize each config files (bash, zsh, fish, vim and emacs) during pearl init command it is better to just configure them when needed, namely when a pearl package containing the respective config file gets added.

As an example, if a package containing config.vim file gets installed, pearl will check whether the pearl init for ~/.vimrc exists and change it accordingly. This will make all the other program config files unchanged.