Add target platform file

Also make tycho build use it and while we're at it, use Eclipse 4.3
repo instead of the kepler simultaneous release repo.
Cleanup existing code + fix identical line editing

Now identical line editing works by finding all identical lines in the
file rather than taking your selection and trying to edit all the lines
in it as if it's identical. (Less useful, but also less prone to stack
traces.)
Update readme