add a non-nul URL for ASF "help", to keep AS7 conversion process happy

optiboot/AtmelStudio/xplained168pb.cproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <SchemaVersion>2.0</SchemaVersion>
@@ -31,7 +31,7 @@
         <options />
         <configurations />
         <files />
-        <documentation help="" />
+        <documentation help="https://github.com/Optiboot/optiboot/wiki" />
         <offline-documentation help="" />
         <dependencies>
           <content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.21.0" />

optiboot/AtmelStudio/xplained328p.cproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <SchemaVersion>2.0</SchemaVersion>
@@ -31,7 +31,7 @@
         <options />
         <configurations />
         <files />
-        <documentation help="" />
+        <documentation help="https://github.com/Optiboot/optiboot/wiki" />
         <offline-documentation help="" />
         <dependencies>
           <content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.21.0" />

optiboot/AtmelStudio/xplained328pb.cproj

@@ -31,7 +31,7 @@
         <options />
         <configurations />
         <files />
-        <documentation help="" />
+        <documentation help="https://github.com/Optiboot/optiboot/wiki" />
         <offline-documentation help="" />
         <dependencies>
           <content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.21.0" />