update description, order by, and hidden keypath (Velocidex#1527)

updated description to include some limitations and also by default it will sort by LastExecution (unsure how this will affect hunts, but im guessing youd need to still order by lastexecution if run as a hunt)

Also added a hidden KeyPath value as that may be valuable (executable v lnk execution)

artifacts/definitions/Windows/Registry/UserAssist.yaml

@@ -12,6 +12,13 @@ description: |
 
   From a forensics perspective, being able to decode this information
   can be very useful.
+  
+  Limitations: Additional data not parsed by Velociraptor is the FocusTime 
+  and FocusCount however these are not reliable. 
+  Also please note that some methods of viewing an executable will update 
+  the associated UserAssist key, and some methods of accessing an executable 
+  will not update the execution counter or time. Therefore there may be 
+  some executions that have a 0 time and 0 runcount.
 
 reference:
   - https://www.aldeid.com/wiki/Windows-userassist-keys
@@ -21,7 +28,7 @@ precondition: SELECT OS From info() where OS = 'windows'
 parameters:
   - name: UserFilter
     default: ""
-    description: If specified we filter by this user ID.
+    description: If specified we filter by this username.
     type: regex
 
   - name: ExecutionTimeAfter
@@ -44,7 +51,7 @@ export:
 
 sources:
   - query: |
-      LET TMP = SELECT parse_string_with_regex(
+      LET TMP = SELECT url(parse=FullPath).Fragment as _KeyPath,parse_string_with_regex(
                 string=url(parse=FullPath).Fragment,
                 regex="^.+Count\\\\\"?(?P<Name>.+?)\"?$") AS Name, FullPath,
              parse_binary(
@@ -58,14 +65,15 @@ sources:
                regex="Users/(?P<User>[^/]+)/NTUSER").User AS User
       FROM Artifact.Windows.Registry.NTUser(KeyGlob=UserAssistKey)
 
-      LET UserAssist = SELECT if(condition=Name.Name,
+      LET UserAssist = SELECT _KeyPath,if(condition=Name.Name,
                    then=rot13(string=Name.Name),
                    else=url(parse=FullPath).Fragment) AS Name,
                User,
                timestamp(winfiletime=ParsedUserAssist.LastExecution) As LastExecution,
                timestamp(winfiletime=ParsedUserAssist.LastExecution).Unix AS LastExecutionTS,
                ParsedUserAssist.NumberOfExecutions AS NumberOfExecutions
         FROM TMP
+        ORDER BY LastExecution
       LET A1 = SELECT * FROM if(
           condition=UserFilter,
           then={