CRA-543 Estimate variables in the bounding model

Has not been tested, as well->getPorosity(dymmy) not can be implemented before multizone inversion is ready.
CRA-562 Include trend parameters s1 and s2 in BlockedLogsForRockPhysics
CRA-563 Variables in the rock physics models should not be estimated in 4D
CRA-534: 2D interpolation almost complete.
CRA-534: Fixed merging conflicts.
CRA-534: Some small changes to 2D interpolation and fixed Makefile under Ubuntu.
CRA-534: Some small changes to 2D interpolation and included WriteToFile() in the class DistributionWithTrendStorage.
CRA-534: Some small changes in 2D interpolation.
Merge branch 'master' of https://github.com/CRAVA/crava
CRA-534: Include methods for 1D trend and variance estimation.
CRA-534: Some small changes and comments.
CRA-534: Some updates and comments to the CRAVA_user_manual.tex.
CRA-635: Implementation of Spearman correlation and fixed some bugs.
Merge pull request #48 from gudmund-hermansen/master

Estimate trend variables.