refactor(generator): remove non-default generators

Sindre Sorhus ‏@sindresorhus:
"@edouard_lopez no default generators anymore"
https://twitter.com/sindresorhus/status/347268486420107264

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
feat(yo,generator): add function at plugin loading to list available generator

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
feat(yo): call function to list (global) generator at startup

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
fix(file,permission): restrict rights to generators list

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
chore(git,ignore): add generators-list.txt to ignore list

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
style(comment): add section ALIAS to yeoman.plugin.zsh

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
fix(generators-list): keep only generator

Previous regex was keep all modules~

Signed-off-by: Édouard Lopez <dev+git@edouard-lopez.com>
refactor(generator-list,variable): define global variables

* Location of this plugin: $__yeoman_pluginDir
* location of generator-list file: $__yeoman_generatorListFile

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