Split into three separate projects: library, gui and cmd

What I have done here:

* Move into different directories
* Split up CMakeLists
* Moved some files correctly into lib or gui that were in the wrong binary before.
* owncloudcmd is finally correctly announcing itself as the binary it is in branded versions
* Removed mirall/ prefix from all includes

Still TODO:

* Test & fix build on OS X and Windows
* More cleanup in the CMakeList.txt files (i.e. aggregate duplicated defines)
* Fix the krazy target

Up for discussion:

* Should library headers be included as `libsync/foo.h` instead of  `foo.h`?
* How to go from here to pull out the GUI dependencies out of libsync
* How to split the translations (lib vs app).

This is not yet meant to be merged for real, but I'd like some feedback.

@dragotin @guruz @ogoffart