Updated the install-VS2015.bat file

> Added two messages :
   * For the build completed successfuly
   * For the Cosmos Builder Tool does not exists

install-VS2015.bat

@@ -1,16 +1,26 @@
-@REM Delete so if builder fails it wont exist
+@REM This file is used to build the Cosmos sources.
+
+@REM This label is used for the 'error1' label if the user trying again.
+:retry
+cls
 del source\Cosmos.Build.Builder\bin\Debug\Cosmos.Build.Builder.*
 
 "%ProgramFiles(x86)%\MSBuild\14.0\Bin\msbuild.exe" "source\Builder.sln" /nologo /maxcpucount /p:Configuration=Debug /p:Platform=x86
 
-@if not exist source\Cosmos.Build.Builder\bin\Debug\Cosmos.Build.Builder.exe goto error
-
+if not exist source\Cosmos.Build.Builder\bin\Debug\Cosmos.Build.Builder.exe goto error1
 start source\Cosmos.Build.Builder\bin\Debug\Cosmos.Build.Builder.exe -bat -VS2015 %1 %2 %3 %4 %5 %6 %7 %8 %9
 
+@REM This is the message for the building successfuly completed.
+@echo -----------------------------------------
+@echo Building done. Press any key to close the window.
+@pause
 @exit
 
-:Error
-@echo _
-@echo _
-@echo Something went wrong.
-@pause
+@REM This is the message if the Cosmos Builder Tool does not exists
+:error1
+@echo -----------------------------------------
+@echo Error: The Cosmos Builder Tool (from source\Cosmos.Build.Builder\bin\Debug\Cosmos.Build.Builder.exe) does not exists.
+@echo Press any key to try again.
+@pause
+@REM At this moment, when the user press any key, it will go to the 'retry' label.
+goto retry