Revert "upgrade reactor promise to latest snapshot API"

This reverts commit 5738eb6ead7ed2e9451bdfe247e9aeb088121fd4.
Revert "revert reactor as dependency doesn't seem to be solved :("

This reverts commit e94c3d226ac90712a39294e52991c0d48aabb961.
Revert "uncomment Reactor factory - trigger hudson"

This reverts commit 9c7de5e58119068889908510ae978563c418dbd9.
Revert "add reactor - promise support"

This reverts commit 0e4f32525fa777ec5fb3f0a554d29540d0de8144.

Conflicts:
	grails-async/build.gradle
	grails-async/src/main/groovy/grails/async/Promises.groovy
	grails-async/src/test/groovy/grails/async/SynchronousPromiseFactorySpec.groovy