Patch by Mitten.O improving tech tree arc caching and moving the arc drawing logic into a separate file.

CMake lists, MSVC and Xcode project files updated accordingly.

git-svn-id: svn://svn.code.sf.net/p/freeorion/code/trunk@7805 dbd5520b-6a0a-0410-a553-f54834df5b05