Merge pull request #1191 from van51/develop

Changed display messages
EigenSolver added, implementation using Eigen3 added
minor changes in EigenSolver, LinearSolver
Merge pull request #1192 from lambday/feature/log_determinant

EigenSolver added, implementation using Eigen3 added
linspace unit test
Merge pull request #1193 from iglesias/develop

linspace unit test
Basic classes