[LU-269] Update core SDK to v2.2.5

Updates to v2.2.5 and uses Gradle plugin v1.0.0. Although the upcoming v2.3.0 release officially adds Gradle 1.0 support, the already-published v2.2.5 works as well. Also updates the instructions and avoids copying resource files.

JIRA issue: [LU-269](https://levelup.atlassian.net/browse/LU-269)
This was added. The rest of the diff in this file is the result of alphabetizing.