Implement pagination in project list screen

The project list screen was taking a long time to render over a large
amount of projects (1,000+) and with even larger number of projects
(3,000+), it could make the browser unresponsive.

Project list screen now uses pagination to resolve this issue. The
number of projects displayed is determined by the 'Maximum Page Size'
user preference.

Bug: issue 2215
Change-Id: Icd0a7d54fd5c5b3c2301c31026e7c6717a648a24

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AdminConstants.java

@@ -130,4 +130,7 @@ public interface AdminConstants extends Constants {
   String sectionTypeReference();
   String sectionTypeSection();
   Map<String, String> sectionNames();
+
+  String pagedProjectListPrev();
+  String pagedProjectListNext();
 }