Update tab claims that parameter groups with all CONST are being localized, i.e., updated

[dafeda]

To reproduce
Steps to reproduce the behaviour:

1. Add new GEN_KW to poly.ert with all CONST.
   For example: GEN_KW COEFFS_CONST coeff_priors_const where the file coeff_priors_const contains:

a CONST 0
b CONST 2
c CONST 5

3. Run Ensemble smoother with Adaptive Localization which results in this screenshot:

Expected behaviour
Make it clear to users that we are not updating const-parameters.

[oyvindeide]

This is intended behavior, so removing the bug label, have added documentation to how one can avoid updating parameters.

[oyvindeide]

Note quite sure what to do with this issue, as it is intended behavior, and the parameters are updated, but still show up as constant for the user. There is no system to allow for not updating single parameters, only parameter groups. So in this particular example the user could add: UPDATE:FALSE, but if one of the parameters were not CONST, that would not work. We could of course add the option of providing UPDATE:FALSE to individual parameters, but that would be quite a bit more work.

[oyvindeide]

So after discussion the solution here is to introduce an UPDATE:TRUE/FALSE flag to individual parameters (as opposed to parameter groups which already exists). If the parameter is CONST, this flag should always be FALSE.