Add a functor MatOp and ScMatrix methods for scalar-matrix operations,
both unary and binary. It can be used for operations which modify each
element for the matrix (in constrast to accumulating ones, like ScGCD
or ScAmpersand).

Split method for addition and substraction into two methods for
consistency and simplicity.

Change-Id: Ic040233429ee120ac325d7baf31a70bba232041d
Reviewed-on: https://gerrit.libreoffice.org/14749Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>