fix coding errors in test class
Ignore gradle.properties file
Fix unit test: set explicit file encoding on reading file content
Make implementation of GFileUtils.mkdirs() more robust on windows
Suppress C++ integTests when no tool chain available
Set custom version number

* set version to "1.8-F-1"
* ignore failing FunctionalReleaseNotesTest
Update unit tests for task graph/plan executors:
 * fix name of DefaultTaskGraphExecuterTest to DefaultTaskGraphExecutorTest
 * move unit tests targeting DefaultTaskPlanExecutor to dedicated test class
 * extract common code of DefaultTaskGraphExecutorTest and DefaultTaskPlanExecutorTest to helper class ExecutorTestHelper
Fix naming: executer --> executor

* rename TaskGraphExecuter to TaskGraphExecutor
* rename DefaultTaskGraphExecuter to DefaultTaskGraphExecutor
* rename related fields accordingly