[handbook] Update for 3.0

Closes #484

See merge request !1338

(cherry picked from commit b0ce2d5a)

9a28187b [handbook] rename domain G to Omega
30ead698 time discretization
f19d0dc0 [handbook] Add link to DUNE cheatsheet.
a81c7e71 [handbook] Update structure and folder setup
46a6e2e6 [handbook] Update parameter section
f8021fa7 [handbook] Move passage about guidelines and delete .tex file
aeacd3d6 Mention where 'actual equations' can be found.
a65a0bb4 [handbook] Modify section on staggered grid discretization.
602eb230 [Handbook] replace tutorial section with dumux course reference
e818ce99 [handbook] updated 'getting started' chapter, split in 'quick start' and…
ed726526 [handbook] Update external modules list
6ea7a2d7 [handbook] Update dune-subgrid description in 2_detailedinstall.tex
a4ff23e9 [handbook] Update dune-sub and spgrid in 2_detailedinstall.tex corrected error in last commit
ae990d7c [handbook] Updated dune-subgrid description in 2_detailedinstall.tex
43e9ae6d [bugfix] Make handbook compile again
2ad6ee7d [handbook] update section on propertysystem to new syntax
4a4e3eaf [doc][handbook] Improve text on property system
b5e780f3 [handbook] Add passage about TTag inheritance order
5cfd24af Add the first draft of parrallel section
b16bd7ab Add the section input and outout
b411ac0a Add the section parralel
b0137f18 Finish the parallel and the input/output section.
747fa637 Add "Costumize the VTK output"
cb612777 [Handbook][Grids] remove external grid section, replace with paragraph in grid format subsection
88eb807a [handbook] Revise stepsofasimulation.
93ef16b6 [handbook][course] cleanup course text to match correct tag reference
02f42fc7 [handbook][3_course] add release tag for dumux-course and cleanup
7677fb70 [handbook][3_course] cleanup
8d47510a [handbook] Update CMakeLists for new tex-files and images
fc5fb34a [handbook][dalton] better image quality
a8e771ec [handbook][4_newfoldersetup] cleanup
1dabc408 [handbook] remove all mentioning of tutorial
74cc4fa9 [handbook][cleanup] Replace \ by \par.
2887b292 [handbook] Introduce to 3.0 and add link to wiki
8f4d1922 [temporal discretization]
68b884db [temporal discretization]
8a77e5e4 [handbook][gnuplot] cleanup
c0f0eec5 [handbook][io] cleanup gnuplot
9541a0b2 [handbook] Update box description
eb9ea429 [handbook][disc] Correction of indices used for the box method
aaf245dc [handbook][disc] Use mpfa stuff from Dennis
132fbb01 [handbook][disc] Add first draft of TPFA description
8ac05303 [handbook][disc] Add first draft of MPFA description
928687f8 [handbook][disc] Update tpfa description and general statements
bb148e5b [handbook][disc] Cleanup mpfa
0b1efc32 [handbook][box] Replace V_j by |B_j|
a900006d [handbook][disc] Use dx d\Gamma consistenly for integrals
11469e1c [handbook][box] Replace wrong scalar products in integrals
6808e8d1 [handbook][pics] Apply renaming of png folder
ac702b5e Merge branch 'feature/improve-handbook-discretization' into 'feature/improve-handbook'
3ab21f73 [handbook] Correct some mistakes in input/output and parallel
3b2dd5a3 [handbook][io] cleanup
a2db2fbc [handbook][parallel] cleanup
067ca3db [handbook][parallel] exceptions multidomain and freeflow
5cb67f60 [handbook] Update input output
824eb40b [handbook] Update parallel
ffa020ef Merge branch 'feature/improve-handbook_inoutput-parallel' into 'feature/improve-handbook'
719b48e0 [handbook] Add small section on restart
12829a9b Update contributors