Introduce basic logic HBS helpers

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+- Start Date: 2016-07-16
+- RFC PR: (leave this empty)
+- Ember Issue: (leave this empty)
+
+# Summary
+
+Introduce the following HandleBars helpers to Ember.js:
+
+ - `{{eq}}`
+ - `{{not-eq}}`
+ - `{{not}}`
+ - `{{and}}`
+ - `{{or}}`
+
+# Motivation
+
+The proposed helpers are some simple helpers that help adding basic logic to
+templates. They are currently already available in an addon called
+[ember-truth-helpers](https://github.com/jmurphyau/ember-truth-helpers), but I
+believe these helpers are essential, because the `ember-truth-helpers` addon is
+one of the most downloaded non Ember CLI default addons.
+
+# Detailed design
+
+See [ember-truth-helpers](https://github.com/jmurphyau/ember-truth-helpers)
+repo for the detailed design of the helpers.
+
+# How We Teach This
+
+The mandatory documentation should be sufficient to teach this to new users.
+Optionally a section in the templates guides could be dedicated to the new logic
+helpers.
+
+# Drawbacks
+
+The only drawback I see is that it expands the surface of the API.
+
+# Alternatives
+
+An alternative could be making `ember-truth-helpers` one of the default addons
+included when generating a new app/addon.
+
+# Unresolved questions
+
+There are no unresolved questions at this time.