Replaces remaining {{category-chooser}} by {{category-select-box}}

To achieve replacement, this commit also adds support for:
- clearSelectionLabel which will allows to unselect any chosen category
- select-box inside a modal
- fixes minor css positioning issues

Note: {{category-chooser}} will be removed in the next weeks.

test/javascripts/acceptance/category-edit-test.js.es6

@@ -74,11 +74,12 @@ QUnit.test("Subcategory list settings", assert => {
   });
 
   click('.edit-category-general');
-  selectDropdown('.edit-category-tab-general .category-combobox', 2);
+
+  selectBox('.edit-category-tab-general .category-select-box', 'feature')
 
   click('.edit-category-settings');
   andThen(() => {
     assert.ok(!visible(".show-subcategory-list-field"), "show subcategory list isn't visible for child categories");
     assert.ok(!visible(".subcategory-list-style-field"), "subcategory list style isn't visible for child categories");
   });
-});
+});

test/javascripts/acceptance/queued-posts-test.js.es6

@@ -20,7 +20,7 @@ QUnit.test("For topics: body of post, title, category and tags are all editbale"
   andThen(() => {
     assert.ok(exists(".d-editor-container"), "the body should be editable");
     assert.ok(exists(".edit-title .ember-text-field"), "the title should be editable");
-    assert.ok(exists(".category-combobox"), "category should be editbale");
+    assert.ok(exists(".category-select-box"), "category should be editbale");
     assert.ok(exists(".tag-chooser"), "tags should be editable");
   });
 });
@@ -41,7 +41,7 @@ QUnit.test("For replies: only the body of post is editbale", assert => {
   andThen(() => {
     assert.ok(exists(".d-editor-container"), "the body should be editable");
     assert.notOk(exists(".edit-title .ember-text-field"), "title should not be editbale");
-    assert.notOk(exists(".category-combobox"), "category should not be editable");
+    assert.notOk(exists(".category-select-box"), "category should not be editable");
     assert.notOk(exists("div.tag-chooser"), "tags should not be editable");
   });
 });

test/javascripts/components/select-box-test.js.es6

@@ -222,7 +222,7 @@ componentTest('persists filter state when expandind/collapsing', {
 });
 
 componentTest('supports options to limit size', {
-  template: '{{select-box width=50 maxCollectionHeight=20 content=content}}',
+  template: '{{select-box maxCollectionHeight=20 content=content}}',
 
   beforeEach() {
     this.set("content", [{ id: 1, text: "robin" }]);
@@ -233,7 +233,6 @@ componentTest('supports options to limit size', {
 
     andThen(() => {
       assert.equal(find(".select-box-body").height(), 20, "it limits the height");
-      assert.equal(find(".select-box").width(), 50, "it limits the width");
     });
   }
 });