Initial implementation of public/internal tasks visibility support
Cache the job fetching the model such that no new jobs scheduled.
Add/Remove model listeners when project changes in the tasks view
Merge branch 'master' into tasks_visibility
Merge branch 'master' into tasks_visibility
Merge branch 'master' into tasks_visibility

Conflicts:
	org.springsource.ide.eclipse.gradle.core.test/src/org/springsource/ide/eclipse/gradle/core/test/GradleProjectTest.java
	org.springsource.ide.eclipse.gradle.core/src/org/springsource/ide/eclipse/gradle/core/GradleProject.java
	org.springsource.ide.eclipse.gradle.core/src/org/springsource/ide/eclipse/gradle/core/modelmanager/IGradleModelListener.java
	org.springsource.ide.eclipse.gradle.core/src/org/springsource/ide/eclipse/gradle/core/modelmanager/ToolinApiUtils.java
	org.springsource.ide.eclipse.gradle.core/src/org/springsource/ide/eclipse/gradle/core/util/GradleProjectIndex.java
	org.springsource.ide.eclipse.gradle.ui.taskview/src/org/springsource/ide/eclipse/gradle/ui/taskview/TaskTreeContentProvider.java
Merge mistake reverted
Fetch BuildInvocations model just for the sake of getting visibility
property. Use EclipseProject model to list tasks.
Backward compatibility support for visibility (all tasks public if
feature not supported)
Cleanup
Added explanation comment
Robustness, wording for logged messages, more API for getting models of
specific type on GradleProject
Include BuildInvocations model data into GradleProjectIndex. Tasks
editor content assist proposals have public/internal task icons.
Merge branch 'master' into tasks_visibility
Support multiple selection for play button in the Gradle Tasks view
Merge pull request #64 from spring-projects/tasks_visibility

Tasks visibility - adoption of BuildInvocations model