VectorOperator checks if number of arguments is valid

The logic to check whether or not the number of arguments is valid has not
yet been implemented. It will be implemented in the isValidArgumentLength
method of VectorOperator.

If the argument length is invalid an exception is thrown. The message of
which includes an expected usage String that must be provided by each
concrete subclass of VectorOperator.

This commit contains build errors in the VectorOperator subclasses.
Added expected usage Strings to all VectorOperators
Implemented argument length checks in VectorOperator

Each VectorOperator contains a Set of accepted argument lengths that
gets filled in the implementations of an abstract method of VectorOperator.

If the argument length provided from the input is contained within the set
then the input is accepted and passed onto the operator for calculation.
Otherwise an exception is thrown.
Log operator can accept any length of argument

Changed infinite argument constant to be Integer.MAX_VALUE.
NodeFunctions's transformer converts itself to vector form

When the .toNodeVector of a NodeFunction's transformer is called, a vector
containing the function itself is returned instead of a numerical evaluation
of the function.
Converted NSolve operator to a VectorOperator
Removed duplicate code in NSolve

Fixed bug in VectorOperator where NodeFunction was being evaluated to a
number causing an exception. Instead the type of the object is tested to see
if it is a NodeNumber.
Conveted Solve operator to a VectorOperator

Modified exception message in VectorOperator if argument length is invalid.

Much duplicate code has been removed in both Solve and NSolve as a result
of them becoming VectorOperators.
Modified NodeFunctions transformation to a NodeNumber

If the argument length of the function is greater than zero (the function
has arguments) then an exception is thrown as the function cannot be
implicitly converted to a number without a value being provided for the
argument.

This modification improves the error messages recieved as otherwise
parse exceptions would be thrown when the function could not be evaluated.

Fixed #1
Removed buggy polynomial package and Complex number class