Merge pull request #316 from sbriseid/install_info

Updated INSTALL file with Windows info. Updated sisl ref.

Author: sbriseid

INSTALL

@@ -15,9 +15,9 @@ To clone the GoTools module, run:
 
 $ git clone --recursive https://github.com/SINTEF-Geometry/GoTools.git
 
-Next the submodules must be initialized:
+Alternatively use ssh:
 
-$ git submodule update --init
+$ git clone --recursive [email protected]:SINTEF-Geometry/GoTools.git
 
 The branch 'master' is the only branch. Any releases will be available as tags.
 
@@ -61,6 +61,16 @@ Windows
 
 The code has been tested using Visual Studio 2015 and 2019, with x64.
 
+Make sure that your installment of Visual Studio includes support for Visual C++. When installing Visual
+Studio you should select "Desktop development with C++" from the Workloads options. If you did not do
+that then you must launch the Visual Studio installer and select "Modify", then select "Desktop
+development with C++". Follow further instructions.
+
+How to edit environment variables:
+- Open the settings application.
+- Search for env, select: "Edit the system environment variables" (or "Edit environment variables for
+  your account" to add them to your user only).
+
 Boost:
 - Download a binary release for your Visual Studio version.
 - To help CMake find the boost install folder the BOOST_ROOT variable must be added to the system