Fix warning about shadowed parameter
Remove constness from onParameterUpdated

Yeah, the problem is that in this method, the observer probably wants to do
some work which would involve changing its internal state, so as nice as it
would be to keep a const pointer to this object it cannot be so.
Tests for min/max/default value
Add parameter type, corresponding tests
Typedef for parameter observer map
Fix potential segfault in removeObserver
Add clear() method for PluginParameterSet

Fixes issue #4.
Parameters can now have a display unit

Resolves issue #2.
Display frequency in kHz when >1000

Fixes #5
Fix compiler error on Xcode
Fix a naggy compiler warning
Parameters can now have display precision

Fixes issue #3
Add some spacing between methods
Add string parameter type

Fixes issue #6.