Initialize peak controller last sample with base value

[LostRobotMusic]

This change makes it so that when an LMMS project is loaded, each knob connected to a Peak Controller will be set to the Peak Controller's Base value, rather than its minimum possible value.

[husamalhomsi]

No need for the comment because the variables names' are descriptive enough.

[Wallacoloo]

@douglasdgi Thanks for the bugfix!

I'm going to go ahead and cherry-pick this onto master as well.

[DomClark]

This doesn't work because the state of the controls has not been restored at the point where m_lastSample is initialised. The effect of this PR is that instead of initialising the value to 0, it is initialised to 0.5, the default value of the base model. This isn't a bad change, since the variable now has the correct initial value upon creation of a new peak controller, but it isn't the desired change either.

A working approach would be either to set m_lastSample from PeakControllerEffectControls::loadSettings after the settings for m_baseModel are loaded:

void PeakControllerEffectControls::loadSettings( const QDomElement & _this )
{
	m_baseModel.loadSettings( _this, "base" );
	m_effect->m_lastSample = m_baseModel.value();
...

or to override loadSettings in PeakControllerEffect, something along the lines of

void PeakControllerEffect::loadSettings( const QDomElement & _this )
{
	Effect::loadSettings( _this );
	m_lastSample = m_peakControls.m_baseModel.value();
}

[PhysSong]

@DomClark I believe newly created peak controllers still need the old change.

[DomClark]

I believe newly created peak controllers still need the old change.

I agree, although it seems less important: changes to a new peak controller's controls don't have an effect on its output until some audio goes through it, so while it would give it a correct initial value, as soon as the user changes the base value it would be incorrect again.