fixed windows path separator

(cherry picked from commit 8401fa00a40294940e43b36169673b97cdd39d29)
fixed PY-12723 Unable to run tests with Django 1.7b1: "RuntimeError: App registry isn't ready yet."

(cherry picked from commit cb808a6abda77ebcef016e65ade98847af2ff02a)
fixed PY-12543 Project Interpreters: too big or too small details popup

(cherry picked from commit 1167e9614ac8b7c70b6c77bfffbd4d2087b56687)
fixed possible NPE

(cherry picked from commit f2b136a8e20c2ba02fcdf014883954d9cde9a7ff)
fixed possible NPE

(cherry picked from commit 5bb996437e608e3d24df16c55c85d2ccc6780e9f)
fixed PY-12451 Interpreter added from project creation dialog is not set as project interpreter

(cherry picked from commit 1be60010739f59157f4ddd344a3878396f33471f)
Use tree set to store remote roots to avoid duplicates.

(cherry picked from commit 3a14f0aa520d83e814f81f081eb150691f9cb823)