IDEA-108615 Gradle: Add 'recent tasks' control

Correct recent tasks control representation
IDEA-104500 Gradle: Allow to reuse common logic for other external systems

Don't check for build.gradle file existence at ide integration because it seems that gradle uses 'virtual projects' internally in case of multi-projects. Example: $GRADLE_HOME/samples/java/multiproject/settings.gradle defines 'include "shared", "api", "services:webservice", "services:shared"' and virtual 'services' project is created. Target directory doesn't contain build.gradle though
IDEA-108602 Gradle: Integrate 'debug task' to the execution system

Trimming vm options before distributing them to the gradle api. It seems that the later is rather fragile in a way that it fails if the options starts with white space
IDEA-108602 Gradle: Integrate 'debug task' to the execution system

Distinct runner id is specified for ExternalSystemTaskDebugRunner
IDEA-104500 Gradle: Allow to reuse common logic for other external systems

Do show external system tool window after initial import from external system
IDEA-104500 Gradle: Allow to reuse common logic for other external systems

Apply gradle home used last time on 'import from gradle' for subsequent imports by default