Add Methcla::Value constructor for double and const char*
Add audio bus id allocator to Methcla::Engine
Add freeNodeIdHandler that calls a function when commpleted
Add port descriptor convenience functions to C++ plugin interface
Add AST envelope synth class
Increase sleep time before retrieving node tree statistics
Store pointer to next node before processing the current one

The current one might destroy itself during the call to process.
Move node done action logic from Synth to Node

Defer the deletion of a node to the next processing cycle in order
to avoid clicks and dangling pointers.
Build: Update stir and replace lens by fclabels
Build: Update stir and build it as a library
Rename shakefile to stirfile