Find certificates in stores by thumbprint or name

- Specify two new command line options and rename some others to make
  finding a certificate in a Windows certificate store more reasonable.

  The new options for loading from a certificate store are:
      --certificate-store-location
      --certificate-store-name
      --certificate-thumbprint
      --certificate-subject-name

  To use these options we require at least a store name, and one of
  thumbprint or subject name. If both thumbprint and subject name are
  specified, we use the thumbprint. If a certificate store location is
  specified that will also be used, otherwise we work as before.

  In addition the options to load a certificate from a file on disk are
  still there:
      --certificate-file
      --certificate-password
Merge pull request #117 from EventStore/certificate-stores

Find certificates in stores by thumbprint or name