Redo templates with docs and whatnot

This totally breaks compatibility with rebar2, and maybe it shouldn't
have.
Allow to forcibly overwrite files with templates
First unkeyed var is now 'name', appid -> name

The first variable can be unkeyed and the provider will sub in the
variable name 'name'. Additionally, the built-in templates and
documentation have been updated so that 'appid' is now 'name' and the
alternative commands are shown.
Merge pull request #28 from tsloughter/templates-redux

Redo templates with docs and whatnot