refactor(yo,helper): move code to helpers_yo so it can be shared

* yeoman.plugin.zsh and _yo need to access same method
* allows yeoman.plugin.zsh to build global information at startup

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
feat(yo,helpers): export path to plugin and generators-list file to global scope

Allow to import helpers in _yo autocompleter ;

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
style(yo,helper): move __yo_getGenerators upward

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
refactor(plugin,yo,helper): rename __yo_getGlobalGenerators to __yo_setGlobalGenerators

It's a setter run once at start-up. Plus update method doc.

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
feat(yo,helper): add 'webapp' to blacklist

It already hardcoded so don't need to display it again

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
style(space): trim

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
fix(yo,helpers): quote accordingly to context

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
refactor(helpers_yo): rename $suggestion -> $metadata

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
style(helpers_yo): remove unused variable ($keywords) and code

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
docs(__yo_getSuggestion): update procedure doc

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>