MockObservations plugin generators

[pazbardanl]

MockObservations plugin generates mock data to be used as inputs when testing other plugins.
Its design is open, allowing development of various types of generators.

Examples of existing generators:

1. CommonGenerator - generates the same key-value pairs of data for all mocked observations.
2. RandIntGenerator - generates a random integer for a user-defined key for all mocked observations (with each observation having a different random value)

Examples of ideas for new generators:

1. Sine generator: generate a sine like signal, based on period (T), offset and and an amplitude. Can optionally have a random seed to create a noise effect.
2. Step function
3. Saw-tooth signal
4. Incremental (linear, quadratic, log...)

Impact:
The more generators we have handy, the more the MockObservations plugin can be used to mock all sorts of inputs: from system metrics (like CPU utilization) to natural signals and inputs.