CustomLv2Host: refactoring

* Move comments.
* Delete exe customLv2SearchPlugins.
CustomLv2Host: update audioBuffer from short to float
CustomLv2Host: update buffer management

* Lv2Graph manages all buffer.
* Can connect a node to a buffer (input or output).
* Add setup fonction for the graph.
* Warning : the output file is silence... (problem with nodes process).
CustomLv2Host:fix nodes process

* The output file is OK (not just silence).
* Audio Buffer -> back to short.
* The process is a reverb.
CustomLv2Host: can process a graph with unconnected nodes
CustomLv2Host: audioBuffer are vector of float
CustomLv2Host: can proces graph with several nodes

* Update graph: gain -> gain -> reverb -> limiter.
* Tmp solution for connect(Node&, Node&): need to create a buffer in the
function instead of create all buffers at the beginning.