Merge branch 'release/0.2' into dev
Update version to 0.3-SNAPSHOT
Add method for impersonating user by user ID

* Add the method GitLabApiClient#asUser(userId) to create a new API client
impersonating that user and create tests for it in
the test class UserImpersonationTest.
* Subclass GitLabApiClient in ImpersonatingGitLabApiClient for
impersonating users by user ID.
* Remove final from method parameters in GitLabApiClient and change some
methods to final and some to protected to make the class suitable for
subclassing.
Add checks to check if the impersonated user does not exist

* Update ImpersonatingGitLabApiClient to throw UserNotFoundException if
attempting to impersonate a user that doesn't exist and add test cases
for this in UserImpersonationTest.
* Add methods to GitLabApiClient for processing the responses from GET
and POST request in subclasses for custom exception handling.
Add test helper method for creating UTC dates

* Add the class DateHelpers for generating UTC dates for test cases and
update test cases with dates to use the helper class.
* Fix parameter orderering in all remaining assertThat(…) calls.
* Add missing test case to AccessLevelTest for the NONE value.
Update README.md with information about impersonating users by ID

Update the section about impersonating users in README.md to reflect the
new method GitLabApiClient#asUser(userId).
Merged feature/sudo-user into dev
Move gitlab-api-client into a submodule

Create a pom.xml file for the parent project and make the
gitlab-api-client into a submodule of the parent project.
Import gitlab-api-plugin into a submodule

Import gitlab-api-plugin from its repository and make it into a
submodule of the parent project.
Fix license texts and version numbers

Fix the version numbers in child projects and fix license texts with
wrong license holders.
Bump version numbers to 0.3

* Bump all version numbers to 0.3.
* Make gitlab-api-plugin use its own version for its gitlab-api-client.
Update POM files for hosting at jenkins-ci.org

* Add SCM information for all POM files.
* Add distribution management information for all POM files.
* Add developer IDs (at jenkins-ci.org) for all POM files.
* Add URL to the Jenkins wiki page for the POM files for the parent and
the Jenkins plugin.
Change Jenkins version to 1.554.1

Update POM file for gitlab-api-plugin to change the Jenkins version to
1.554.1.
Add description to POM files

* Add description to the POM files of gitlab-api-plugin-parent and
gitlab-api-plugin taken from the index.jelly file of the plugin.
* Add name and description to the POM file of gitlab-api-client
Change groupId to com.sonymobile.jenkins.plugins.gitlab

* Change the groupId to com.sonymobile.jenkins.plugins.gitlab and move
existing packages.
* Change URL for SCM since the parent project is not going to have
"parent" in its folder name.
* Fix package name in config.groovy.
* Fix bug getting the API client from GitLabConfiguration (possibly
introduced when switching to Jenkins 1.554.1).
Add README.md file for the parent module

Add a brief README.md file for the parent module and update README.md
for gitlab-api-plugin with a short usage section.
Merge branch 'release/0.3'