Fixes for invalid NULL sql on date/times

Most files are simple swaps to get rid of extra " as a NULL return will give
invalid SQL if used as follows UPDATE x SET y="NULL";

See github issue 121 for more info.

Extra changes have been made to the following files:
* lib/rdcartslot.cpp
- Added a QDateTime variable to prevent EVENT_DATETIME becoming
  "2016-06-09" "NULL" as it was checked separately for date and time
* lib/rdcut.cpp
- Reworked START_DATETIME and END_DATETIME to save the SQL ifs.  I believe this
  makes it easier to read and understand.
- The >QDate(1900,1,1) and < 8000 is probably not needed but I left it there
  just in case.
* lib/rdescape_string.cpp
- Reworked to add extra " if the date is not NULL see issue 121
* lib/rdfeed.cpp && lib/rdpodcast.cpp
- Had to add a SetRow for QDateTime as with the string conversion the existing
  SetRow would add an extra set of "
* lib/rdsound_panel.cpp && rdairplay/log_traffic.cpp
        && utils/rddgimport/rddgimport.cpp
- Added a QString to contain EVENT_DATETIME to prevent double checks of date
  and time separately (similar to lib/rdcartslot.cpp)
* rdcatchd/rdcatchd.cpp
- Reverted the changes.  The RML here is not touching the DB so is fine, plus
  with the RDCheckDateTime changes you'd have extra " unless it was NULL
* tests/sas_switch_torture.cpp && sas_torture.cpp
- Included missing rdescape_string.h

lib/rdcartslot.cpp

@@ -670,6 +670,8 @@ void RDCartSlot::LogPlayout(RDPlayDeck::State state)
     datetime.setDate(datetime.date().addDays(-1));
   }
   if(!slot_svcname.isEmpty()) {
+    QDateTime eventDateTime=QDateTime::QDateTime(datetime::date(), 
+          slot_logline->startTime(RDLogLine::Actual));
     QString svctablename=slot_svcname;
     svctablename.replace(" ","_");
     sql=QString("insert into `")+svctablename+"_SRT` set "+
@@ -687,19 +689,18 @@ void RDCartSlot::LogPlayout(RDPlayDeck::State state)
 			slot_logline->usageCode(),
 			slot_logline->startSource())+
       "STATION_NAME=\""+RDEscapeString(slot_station->name())+"\","+
-      "EVENT_DATETIME=\""+datetime.toString("yyyy-MM-dd")+
-      " "+RDCheckDateTime(
-    		  slot_logline->startTime(RDLogLine::Actual),"hh:mm:ss")+"\","+
-      "EXT_START_TIME=\""+RDCheckDateTime(
-    		  slot_logline->extStartTime(),"hh:mm:ss")+"\","+
+      "EVENT_DATETIME="+RDCheckDateTime(eventDateTime,"yyyy-MM-dd hh:mm:ss")+
+      ","+
+      "EXT_START_TIME="+RDCheckDateTime(
+    		  slot_logline->extStartTime(),"hh:mm:ss")+","+
       "EXT_DATA=\""+RDEscapeString(slot_logline->extData())+"\","+
       "EXT_EVENT_ID=\""+RDEscapeString(slot_logline->extEventId())+"\","+
       "EXT_ANNC_TYPE=\""+RDEscapeString(slot_logline->extAnncType())+"\","+
       "EXT_CART_NAME=\""+RDEscapeString(slot_logline->extCartName())+"\","+
       "TITLE=\""+RDEscapeString(slot_logline->title())+"\","+
       "ARTIST=\""+RDEscapeString(slot_logline->artist())+"\","+
-      "SCHEDULED_TIME=\""+RDCheckDateTime(
-    		slot_logline->startTime(RDLogLine::Logged),"hh:mm:ss")+"\","+
+      "SCHEDULED_TIME="+RDCheckDateTime(
+    		slot_logline->startTime(RDLogLine::Logged),"hh:mm:ss")+","+
       "ISRC=\""+RDEscapeString(slot_logline->isrc())+"\","+
       "PUBLISHER=\""+RDEscapeString(slot_logline->publisher())+"\","+
       "COMPOSER=\""+RDEscapeString(slot_logline->composer())+"\","+