Update build.rst to match Scala master

Scala master includes much more simplified way of publishing locally. I updated the docs for building IDE against local build of Scala to reflect that.
Docs for the Indent Guide feature
Merge pull request #90 from sschaef/t-indent-guide

Docs for the Indent Guide feature
Adds a comment about where to install Play

Fixes #26
Merge pull request #91 from skyluc/issue/play-installed-on-readonly-location-26

Adds a comment about where to install Play
Adds some extra tweaks on top PR #89
Merge pull request #92 from skyluc/pr-89

Update build.rst to match Scala master
License file from scala-ide copied
Merge pull request #94 from VirtusLab/license-added

License file from scala-ide copied