trigger signal issues handled at acquire (#862)

* if blocking and handling sync, only master gets blocking acq, slaves get non blocking as they are first and so dont get status or error caught when slaves dont get trigger (due to not connected etc) and acq returns with slaves still in waiting status. so check status of all in blocking acq

* for all dets with sync, ensure atleast one master when starting acq

* docs updated about sync

RELEASE.txt

@@ -172,6 +172,16 @@ This document describes the differences between v8.0.0 and v7.0.3
         -   Rearranging digital data when dbit list less than 64 bits fixed.
 
 
+    Client
+    ------
+
+    *   [Jungfrau][Mythen3][Gotthard2] Sync mode should have at least one master
+        Multi module synced detectors should have at least one master when 
+        starting acquisition, else it will throw. Once master is done acquiring
+        (blocking mode), status of all modules checked to ensure none of the 
+        slaves in waiting due to hardware issues such as cabling.
+
+
 
 2.3 New Features
 ================