disable test for GS with multiple iterations, it seems to be broken.

[[Imported from SVN: r1671]]

add new test for real matrices with complex rhs
(patch by Matthias Wohlmuth)

[[Imported from SVN: r1670]]

add identity as precoditioner (mainly for testing purposes)
(patch by Matthias Wohlmuth)

[[Imported from SVN: r1669]]

[[Imported from SVN: r1668]]

make sure 1 is casted to the correct type (fix complex)
(patch by Matthias Wohlmuth)

[[Imported from SVN: r1667]]

[[Imported from SVN: r1666]]

initialize result with 0
(patch by Matthias Wohlmuth)

[[Imported from SVN: r1659]]

Removed two spurious semicolons.
(thanks to Andreas Lauser for the patch)

[[Imported from SVN: r1658]]

[[Imported from SVN: r1657]]

[[Imported from SVN: r1656]]

Changed return type of a void function to void.

[[Imported from SVN: r1651]]

- fix some real_type vs field_type issues
- make more solvers work with complex
(thanks to Matthias Wohlmuth)

[[Imported from SVN: r1650]]

(thanks to Matthias Wohlmuth)

[[Imported from SVN: r1649]]

update multitypeblockvector to distinguish between operator* and dot
(thanks to Matthias Wohlmuth)

[[Imported from SVN: r1648]]

update blockvector to distinguish between operator* and dot
(thanks to Matthias Wohlmuth)

[[Imported from SVN: r1647]]

(thanks to Matthias Wohlmuth)

[[Imported from SVN: r1646]]

[[Imported from SVN: r1645]]

[[Imported from SVN: r1644]]

dune-common. They were deprecated since Dune 2.1.

[[Imported from SVN: r1643]]

[[Imported from SVN: r1642]]

FS#1029 for more details.

[[Imported from SVN: r1641]]

[[Imported from SVN: r1640]]

Patch by Uli Sack

[[Imported from SVN: r1638]]

and ScaledIdMatrix

Patch by Uli Sack

[[Imported from SVN: r1637]]

ScaledIdMatrix or a DiagonalMatrix.

Patch by Uli Sack

[[Imported from SVN: r1636]]

[[Imported from SVN: r1635]]

[[Imported from SVN: r1632]]

[[Imported from SVN: r1631]]

Patch by Andreas Lauser

[[Imported from SVN: r1627]]

[[Imported from SVN: r1626]]

[[Imported from SVN: r1623]]

[[Imported from SVN: r1622]]

[[Imported from SVN: r1620]]

[[Imported from SVN: r1618]]

[[Imported from SVN: r1609]]

[[Imported from SVN: r1608]]

[[Imported from SVN: r1601]]

[[Imported from SVN: r1600]]

[[Imported from SVN: r1599]]

Thanks to Andreas Lauser for pointing this out.

[[Imported from SVN: r1591]]