Revert "Revert "Added DiskEngine.java, DiskPositionalIndex.java, IndexWriter.java""

This reverts commit 787307b5b1f60d4687e51f24a0fd1bda5c6f18e3.
Revert "Fixed bug where an infinity loop started. -Code was attempting to find the next iteration when in fact there was none."

This reverts commit 102eeb95a34dd16873aae21f83727f2eef121c3a.
Revert "Revert "Fixed bug where an infinity loop started. -Code was attempting to find the next iteration when in fact there was none.""

This reverts commit 5d8396e4e251c48322c6193378382a8562df927c.