Remove rcp_core code.
Squashed 'rcp_core/' content from commit f7dc502

git-subtree-dir: rcp_core
git-subtree-split: f7dc502f7adebd8dbfb908c1d9513c6ecc5ac9d7
Merge commit '6c5b2fb5ab3b7e429a212e9a43e060837956c3f4' as 'rcp_core'