update gradlew and gradle plugins

update gradlew to 2.2.1
update com.android.tools.build:gradle to 1.0.0-rc1
update com.github.dcendents:android-maven-plugin to 1.2
update com.jfrog.bintray.gradle:gradle-bintray-plugin to 1.0
change task name "generate${variant.name}Javadoc" to "generate${variant.name.capitalize()}Javadoc" ("generatereleaseJavadoc" to "enerateReleaseJavadoc")
add BINTRAY_USER_ORGANIZATION gradle property
add standalone build.gradle script in library and sample subprojects

add library/build.gradle
add sample/build.gradle