Merged String and Text datatypes

* Use SMWDIBlob instead of SMWDIString
* Use '_txt' instead of '_str'
* Language files updated to use name of "Text" datatype as main, "String" as alias
* For SMW 1.9, '_str' and SMWDIString remain functional as aliases for '_txt' and SMWDIBlob (b/c)
* The Store3 DI handler code for string is now in the file for blobs; the file for strings was removed
  (no b/c issue since it is only an internal helper class of Store3)

Update: fixed typo in one of the language files
Update 2: actually really fixed the typo now

Change-Id: Id8b47413ff7869bc694e651adce11acf0f015a7c
Merge "Merged String and Text datatypes"