- fixed infinite loop in mtimes()

quantity.Discrete & .Symbolic:
- renamed variables in isConstant() to improve readability

I guess fixed uminus in quantity.Function is still buggy.

quantity.Discrete & quantity.Symbolic: plus and minus now support quantity and numeric arrays of same size.

quantity.Symbolic: bugfix in subs() and use of quantity.Symbolic constructor for the result of int()

- solveAlgebraic: adjusted to change of changeGrid from call-by-reference to call-by-value
- diff(): now supports specification of various variables for which the derivative should be applied. Ensured consistency with Symbolic. Maybe a more elegant use of gradient() is possible.
- unittests: adjusted for now behavior of diff()

quantity.Symbolic bugfixes:
- diff(): now supports specification of various variables for which the derivative should be applied. Ensured consistency with Discrete.
- unittests: adjusted for now behavior of diff()

Changed implementation of integration for "Discretes". The input arguments are now consitent with the matlab "int" function.

*) Allow to set empty quantity.Discrete objects with certain size
*) added the isConstant property for the quantity.Discrete
*) Implemented a cast to the quantity.Operator object
*) Implemented a cast of empty quantity.Discretes to quantity.Symbolics
*) Fixed bug in "on()" for constant quantities
*) Fixed some functions to work with empty quantities
*) Added a settings object to use global settings
*) plot function returns now an array of the figure handles
*) Re-implementation of the quantity.Operator object

quantity.Symbolic: Bugfixes in subs and abs, inv, exp, expm... this constructor is really messy for constant values

This functions seemed to be depricated.

- bugfix in get.grid()
- horzcat, vertcat, cat now ensure, that grid and gridName of all quantities to be concatenated are compatible, by changing the grid to the finest grid.

Initial checkin of the matlab library for the control and faultdiagnosis of infinite dimensional systems