Description
    Ramp function base class for the set of scalar functions starting from 0 and
    increasing monotonically to 1 from \c start over the \c duration and
    remaining at 1 thereafter.

    Usage:
    \verbatim
        <entryName> <rampFunction>;
        <entryName>Coeffs
        {
            start     10;
            duration  20;
        }
    \endverbatim
    or
    \verbatim
        <entryName>
        {
            type      <rampFunction>;
            start     10;
            duration  20;
        }
    \endverbatim

    Where:
    \table
        Property | Description  | Required | Default value
        start    | Start time   | no       | 0
        duration | Duration     | yes      |
    \endtable

The following common ramp functions are provided: linear, quadratic, halfCosine,
quarterCosine and quaterSine, others can easily be added and registered to the run-time
selection system.