Modifications to elliptic eigenproblem example

[siuwuncheung]

This is a follow up PR for #266 to enable the followings:

1. Use consistent signs of eigenfunctions
2. Add boundary condition switch
3. Clean up to retain only 4 problems, i.e. poisson, reaction-diffusion in heterogeneous media, Schrodinger equation with harmonic potential, Schrodinger equation with negative Gaussian potential well
4. Extend to 3D examples
5. Change some basis filenames

Results from PR266

Number of unknowns: 289 
Opening file: basis.000000
spatial basis dimension is 289 x 20
Eigenvalue 0: = 0.048430949
Eigenvalue 1: = 0.12021157
Eigenvalue 2: = 0.12147847
Eigenvalue 3: = 0.19456504
Eigenvalue 4: = 0.24285855
Relative error of ROM solution for eigenvalue 0 = 0.068334316
Relative error of ROM solution for eigenvalue 1 = 0.060776586
Relative error of ROM solution for eigenvalue 2 = 0.057586388
Relative error of ROM solution for eigenvalue 3 = 0.069508795
Relative error of ROM solution for eigenvalue 4 = 0.057544708
Relative l2 error of ROM eigenvector 0 = 2.0185057
Relative l2 error of ROM eigenvector 1 = 0.090773417
Relative l2 error of ROM eigenvector 2 = 0.076616931
Relative l2 error of ROM eigenvector 3 = 1.9746465
Relative l2 error of ROM eigenvector 4 = 1.9912245
Unable to connect to GLVis server at localhost:19916
GLVis visualization disabled.
Elapsed time for assembling ROM: 1.319277e-02 second
Elapsed time for solving ROM: 5.071391e-02 second

Results from commit 861bcdb3eb9fa6df97db26a4795957bdbf768c9d

Number of unknowns: 289 
Opening file: basis.000000
spatial basis dimension is 289 x 20
Eigenvalue 0: = 0.048430949
Eigenvalue 1: = 0.12021157
Eigenvalue 2: = 0.12147847
Eigenvalue 3: = 0.19456504
Eigenvalue 4: = 0.24285855
FOM solution for eigenvalue 0 = 0.04533314
Absolute error of ROM solution for eigenvalue 0 = 0.0030978091
Relative error of ROM solution for eigenvalue 0 = 0.068334316
FOM solution for eigenvalue 1 = 0.11332411
Absolute error of ROM solution for eigenvalue 1 = 0.0068874528
Relative error of ROM solution for eigenvalue 1 = 0.060776586
FOM solution for eigenvalue 2 = 0.11486387
Absolute error of ROM solution for eigenvalue 2 = 0.0066145954
Relative error of ROM solution for eigenvalue 2 = 0.057586388
FOM solution for eigenvalue 3 = 0.18192
Absolute error of ROM solution for eigenvalue 3 = 0.01264504
Relative error of ROM solution for eigenvalue 3 = 0.069508795
FOM solution for eigenvalue 4 = 0.22964377
Absolute error of ROM solution for eigenvalue 4 = 0.013214784
Relative error of ROM solution for eigenvalue 4 = 0.057544708
Relative l2 error of ROM eigenvector 0 = 0.070341449
Relative l2 error of ROM eigenvector 1 = 0.090773417
Relative l2 error of ROM eigenvector 2 = 0.076616931
Relative l2 error of ROM eigenvector 3 = 0.10714041
Relative l2 error of ROM eigenvector 4 = 0.14993251
Unable to connect to GLVis server at localhost:19916
GLVis visualization disabled.
Elapsed time for assembling ROM: 6.902814e-03 second
Elapsed time for solving ROM: 5.741106e-03 second