GUI interface still not quite working. Two issues:

* PyQt4.QtSql's SQLite interface doesn't appear to return the same results as the SQLite browser. This is probably me depending on a bad data ordering assumption.
* QSqlQueryModel isn't set up to have the db change from underneath it, AFAIK -- have to add the ability to notify it there's new data.

python/sql.py

@@ -38,7 +38,7 @@ class output_sql:
     c = self._db.cursor()
     query = """CREATE TABLE IF NOT EXISTS "positions" (
               "icao" INTEGER KEY NOT NULL,
-              "seen" TEXT NOT NULL,
+              "seen" DATETIME NOT NULL,
               "alt"  INTEGER,
               "lat"  REAL,
               "lon"  REAL
@@ -46,7 +46,7 @@ class output_sql:
     c.execute(query)
     query = """CREATE TABLE IF NOT EXISTS "vectors" (
               "icao"     INTEGER KEY NOT NULL,
-              "seen"     TEXT NOT NULL,
+              "seen"     DATETIME NOT NULL,
               "speed"    REAL,
               "heading"  REAL,
               "vertical" REAL