Testsuite: Augment feature constraints with version number

Testsuite: Augment feature constraints with version number

Beside the already introduced constraints

  with_feature=(yes|true|on)
  with_feature=(no|false|off)

it is now also possible to specify a version number:

  with_feature=x.y.z

A test with this constraint will be picked up if

 a) deal.II is configured with "feature"

 b) DEAL_II_FEATURE_VERSION is defined (in deal.IIConfig.cmake) and
    DEAL_II_FEATURE_VERSION is "version greater or equal" than "x.y.z"

A version number "x.y.z" must satisfy the regular expression [0-9]+(\.[0-9]+)*