feat($templateFactory): refactor to a Provider to have a $http/$templateRequest switch

[rjamet]

This creates a $TemplateFactoryProvider to be able to set a global config option that forces $templateFactory to use $http (which bypasses the security checks, hence the scary name). Added tests and doc for that too. This still defaults to $http on older Angulars as expected.

Fixes the legacy part of #3193. Let me know if there's style issues or missing doc.

[christopherthielen]

very nice, thanks! Can you fix the three linter errors?

https://travis-ci.org/angular-ui/ui-router/builds/184267215

Running "jshint:all" (jshint) task
Linting src/templateFactory.js ...ERROR
[L164:C2] W032: Unnecessary semicolon.
};
Linting build/angular-ui-router.js ...ERROR
[L613:C16] W055: A constructor name should start with an uppercase letter.
    return new $TemplateFactory($http, $templateCache, $injector, shouldUnsafelyUseHttp);}];
[L729:C2] W032: Unnecessary semicolon.
};

[rjamet]

Yup, done. I removed the $ in the local names, it shouldn't change things since they're still provided with the right names, and that way, they can be lint-compliant constructors.

[christopherthielen]

Thanks very much! Let me know if you want to tackle porting to master. If not, I'll probably do it later this week or weekend.

[rjamet]

Feel free to do it, I don't have much time in the next days. Thanks for maintaining this library!