add --no-init option to gut template generate

[snomos]

When creating a new repo, there should be an option to specify a template repo to pre-populate the new repo with content. When using such a template, also the .gut/ dir should be automatically configured for future delta updates, and all string replacements should be carried out.

This option requires another option: the 3-letter language code. From that code, one can derive the two-letter code (if it exists), and also the English language name.

A variant of the create new repo command is to superimpose the template structure on an existing repo, typically when outside projects would like to use our infra to produce spellers and other tools. The outside repo is transfered to our org, and then needs to be given the same setup as the other languages. Applying or superimposing the template repo content fills that need (with some reorganisation of the exising content afterwards).

I have labelled this with critical-path, as there is a need to have this functionality in place very soon, there will certainly be a need for adding new languages (both completely new and existing outside projects) in the near future, when collaboration with Canada starts for real.

[snomos]

This is also covered in issue #44 but I keep this open, as it contains additional info and use cases.

[snomos]

gut template generate covers this, except that when applied to an existing repo (to introduce GiellaLT specific elements etc to an imported project), the command fails, because it tries to initialise a new git repo.

An option --no-init or something should be available to tell the gut command that it should skip the init phase.