Fixing pitch envelope export and improving auto pitch envelope

[davidhealey]

I've made it so the first and last node of the auto generated pitch envelope is set to 0.5 after the table is reset.

After the table is generated the first node is set to be the same as the second node. I've found in practice that it works out well, rather than leaving it at 0.5.

I've also set it to remove any nodes that are 0.0 or 1.0 because otherwise I've found that the envelope always includes a few random 0s and 1s at the start and end which I was getting RSI from removing :)

I've added optional arguments to set the sample rate and bit depth for the CompressionHelpers::dump function so that when using the Apply sample map properties to sample files tool we can use the sample rate and bit depth of the original samples. When no sample rate or bit depth is provided to the function it will default to 44100/16 which were the previously hardcoded values.