键（key）name 上的 := 方法会返回一个 Setting
http://www.scala-sbt.org/1.x/docs/Plugins-Best-Practices.html
http://www.scala-sbt.org/1.x/docs/Best-Practices.html
SBT_HOME/conf/sbtconfig.txt
-Dfile.encoding=UTF8
-Dsbt.global.base=d:/.sb
-Dsbt.boot.directory=d:/.sbt/boot
-Dsbt.ivy.home=d:/.sbt
-Dsbt.repository.config=d:/.sbt/repositories
环境变量 SBT_OPTS
-Dsbt.global.base=d: oolssbt.sbt -Dsbt.ivy.home=d: oolssbt.ivy2
sbt base 目录下add 文件 repositories
[repositories]
local
taobao: http://maven.aliyun.com/nexus/content/groups/public
taobao-ivy: http://maven.aliyun.com/nexus/content/groups/public, [organization]/[module]/(scala_[scalaVersion]/)(sbt_[sbtVersion]/)[revision]/[type]s/[artifact](-[classifier]).[ext]
repox-maven: http://repox.gtan.com:8078/
repox-ivy: http://repox.gtan.com:8078/, [organization]/[module]/(scala_[scalaVersion]/)(sbt_[sbtVersion]/)[revision]/[type]s/[artifact](-[classifier]).[ext]