SCL-4336 fix in-place rename of back-ticked references

Preserves the backticks in references after the rename.

    class Test {
      def test {
        val yyyy = 1
        val (`yyyy`, 0) = (1, 2)

        val xxxxxx = 0
        xxxxxx
        `xxxxxx`
      }
    }

Previously, I had disabled in place renaming if back ticked references existed (aad00a9f95). That no longer worked after the addition of `ScalaInplaceRenamer`.

This commit adjusts `ScReference#getTextRange` to exclude backticks.

During the fix, I noticed another problem. In the code below, the usage search for `xxxx` comes up empty.

    // File1.scala
    object O {
      val xxxx = 0
    }

    // File2.scala
    object Test {  O.`xxxx` }
Merge pull request #38 from retronym/ticket/SCL-4336

SCL-4336 fix in-place rename of back-ticked references