Add script to generate template effect files

[regulus79]

This PR allows users to generate all the boilerplate code needed to make an effect with a single script, instead of having to manually copy Amplifier and rename everything.

How to use

First checkout this PR

git fetch origin pull/7910/head:generate-effect
git switch generate-effect

Then enter the plugins folder

cd plugins

Run the python script!

>>> python setupeffect.py

Effect Name (UpperCamelCase): TestEffect
Lowercase version: testeffect, Uppercase version: TEST_EFFECT
Effect Name (Human readable, spaces allowed): Test Name
Effect Description: Test Description
Effect Author: Me
Number of knobs: 7
Creating directory /home/user/lmms/plugins/TestEffect
TestEffect template files successfully written to /home/user/lmms/plugins/TestEffect
Updated ../cmake/modules/PluginList.cmake

Then rebuild lmms, and check out your new effect!

You just saved 5-10 minutes of your life! Now you can start developing your effect right away!

[regulus79]

I'm thinking it might be useful to be able to specify what the floatmodels/knobs are called, since it's a bit of a pain to rename them all.