Add widget to allow user to easily, incrementally increase processor baseline frequency

[ayoungethan]

This is a feature request, and an extension of the fact that Cadence has incorporated a convenient control of the computer's CPU governor. It is based on the idea that DSP capacity is entirely dependent on the CPU's lowest frequency.

Here is the design idea (at least for intel CPUs -- not sure if this would work with AMD processors):

1. the control would be a single slider that replaces the CPU governor selection.
2. All the way to the left enables the Intel HWP powersave governor (fully automated CPU scaling, much like the ACPI ondemand governor).
3. All the way to the right enables performance governor.
4. In between allows adjusting the "minimum" frequency parameter, with "sticky" points at the pstate "efficient" and "guaranteed" (TDP) frequencies.

The rationale for this is that

1. CPU frequency scaling happens too slowly to accommodate low latency throughput demands
2. computer users may not need the extra low latency throughput of always running in "performance" mode at the max frequency, and
3. they may not want the extra heat, noise or battery drain that goes with it.
4. A slider would let users easily choose lower baseline frequencies that still offer greater low latency throughput performance than the fully automatic governor, tailored to the workload, while still
5. allowing the CPU to scale to accommodate non-realtime spikes in CPU demand without overloading, and
6. preventing excessive (e.g., fan) noise, heat and/or power consumption.