Added README to master

+# WebServicePlugins
+
+The initial checkin to the master branch is a copy of the original code from
+Codeplex of the VS2013 version of the plugin, taken 2017-09-02.
+
+This project has a master branch for the main logic, and separate branches for
+specific code targeting specific versions of Visual Studio. I.e. code changes
+specific for a VS version should be committed to the appropriate branch. Code
+changes to common files should be committed to master, so the VS specific
+version branches can merge with master to receive these updates, without having
+to cherry pick commits.
+
+This also means that the branches may NEVER be merged into master, since these
+only contain VS version specific code changes.
+
+Builds should only be created on the non master branches, for a specific version
+of Visual Studio, although the master branch currently targets VS2013, there is
+a specific branch for VS2013 as well. Changes that are needed to be committed
+that are specific for VS2013 should therefor be committed to the vs2013 branch,
+since these can not be allowed to be merged into the other version branches.
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