Fixed #352.
Revised document for version 0.6.0 (#340, #346)

* Changes standard build system on documents to Gradle-based.
* Introduction documents use Direct I/O example.
* Makes a many minor improvements.
Fixed #343 document.
Fixed #353.

Enables to modify compilerArgs via build script and changes default
value [Gradle Plugin].
Add internal extension for configuring jobs.
Fixed #355

Adjusts application build log.
Merge remote-tracking branch 'private/issue/340' into 0.6-develop
Merge remote-tracking branch 'private/issue/352' into 0.6-develop
Merge remote-tracking branch 'private/issue/353' into 0.6-develop
Merge remote-tracking branch 'private/issue/354' into 0.6-develop
Merge remote-tracking branch 'private/issue/355' into 0.6-develop
Fixed #356.

Task inputs/outputs property does not evaluate correctly when changing
that [Gradle Plugin]
Adds task input properties evaluation (#356).
Merge remote-tracking branch 'private/wip/issue/356' into 0.6-develop
Refactoring Gradle Plugin (#342).
Merge remote-tracking branch 'private/issue/342-M3' into 0.6-develop
Revised gradle migration document (#340, #346).
Merge remote-tracking branch 'private/issue/340' into 0.6-develop