update splash png to contain border and shadow
Optimise Server#trigger_synth to remove unnecessary method calls
Further synth trigger optimisations:

* reduce function calls where possible.
* Don't add on_started handler to synth node if not necessary
* Reduce number of hash merges required if possible
* always ensure out-bus is correctly set
Add trailing > to to_s for buffer
Create recording group on studio initialise
resolve hash_or_arrah args when controlling node
Extract out allocator from bus allocator:

* Remove all bus specific behaviour - now allocator is a generic id
  allocator to be used in other places such as buffer id allocation
swap attr_reader arg order to match constructor
Teach allocators to have a default index offset of 0
Add default of 1 for Allocator#num_adj_ids
Use Allocator to allocate buffer ids rather than a Counter:

* Allows buffer ids to be recycled
Unify file header comments:

* switch gui/qt/* files to use same header as server code.
Reorder autocompletion code to match sample README order:

* eases comparisons across versions.
Add ability to allocate standard buffers:

* Need to teach buffer infos how to release buffer ids
add Buffer@to_i method - returns buffer id
Add Server#buffer_free - which also releases id from allocator
Add new server arg to Buffer constructor
Implement Buffer#free
Add default number of adjacent ids for Allocator#release!
Add new class BufferStream for streaming buffers to files:

* useful for recording to disk