Added links to the relax wiki, API documentation, and relax website to all dispersion models in the manual.

This is to make it easier to find additional information about each of the models.

For reference, the relax wiki links are:
    http://wiki.nmr-relax.com/R2eff
    http://wiki.nmr-relax.com/No_Rex
    http://wiki.nmr-relax.com/LM63
    http://wiki.nmr-relax.com/LM63_3-site
    http://wiki.nmr-relax.com/CR72_full
    http://wiki.nmr-relax.com/CR72
    http://wiki.nmr-relax.com/IT99
    http://wiki.nmr-relax.com/TSMFK01
    http://wiki.nmr-relax.com/NS_CPMG_2-site_expanded
    http://wiki.nmr-relax.com/NS_CPMG_2-site_3D_full
    http://wiki.nmr-relax.com/NS_CPMG_2-site_3D
    http://wiki.nmr-relax.com/NS_CPMG_2-site_star_full
    http://wiki.nmr-relax.com/NS_CPMG_2-site_star
    http://wiki.nmr-relax.com/MMQ_CR72
    http://wiki.nmr-relax.com/NS_MMQ_2-site
    http://wiki.nmr-relax.com/NS_MMQ_3-site_linear
    http://wiki.nmr-relax.com/NS_MMQ_3-site
    http://wiki.nmr-relax.com/M61
    http://wiki.nmr-relax.com/M61_skew
    http://wiki.nmr-relax.com/DPL94
    http://wiki.nmr-relax.com/TP02
    http://wiki.nmr-relax.com/TAP03
    http://wiki.nmr-relax.com/MP05
    http://wiki.nmr-relax.com/NS_R1rho_2-site
    http://wiki.nmr-relax.com/NS_R1rho_3-site
    http://wiki.nmr-relax.com/NS_R1rho_3-site_linear

The API documentation links are:
    http://www.nmr-relax.com/api/3.1/specific_analyses.relax_disp.optimisation-module.html#back_calc_r2eff
    http://www.nmr-relax.com/api/3.1/lib.dispersion.two_point-module.html#calc_two_point_r2eff
    http://www.nmr-relax.com/api/3.1/target_functions.relax_disp.Dispersion-class.html#func_NOREX
    http://www.nmr-relax.com/api/3.1/lib.dispersion.lm63-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.lm63_3site-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.cr72-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.it99-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.tsmfk01-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.ns_cpmg_2site_expanded-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.ns_cpmg_2site_3d-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.ns_cpmg_2site_star-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.mmq_cr72-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.ns_mmq_2site-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.ns_mmq_3site-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.m61-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.m61b-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.dpl94-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.tp02-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.tap03-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.mp05-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.ns_r1rho_2site-module.html
    http://www.nmr-relax.com/api/3.1/lib.dispersion.ns_r1rho_3site-module.html

The relax website links are:
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#R2eff
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#No_Rex
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#LM63
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#LM63_3-site
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#CR72_full
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#CR72
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#IT99
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#TSMFK01
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_CPMG_2-site_expanded
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_CPMG_2-site_3D_full
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_CPMG_2-site_3D
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_CPMG_2-site_star_full
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_CPMG_2-site_star
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#MMQ_CR72
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_MMQ_2-site
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_MMQ_3-site_linear
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_MMQ_3-site
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#M61
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#M61_skew
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#DPL94
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#TP02
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#TAP03
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#MP05
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_R1rho_2-site
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_R1rho_3-site
    http://www.nmr-relax.com/analyses/relaxation_dispersion.html#NS_R1rho_3-site_linear