Linux: Add nsm support

please consider adding support for nsm (non session manager: )

a session manager makes it easy to work modularly on linux, and this is an attractive alternative to working with monolithic DAWs. among other functions, the session manager starts and stops many clients with a single click, saves and restores the states of clients, allows creation of workflows or templates that incorporate many different tools, and stores everything relevant to a given project in a single directory

for example: my current session has a guide beat in hydrogen, a jack synced video monitor, two mixer groups (separate instances of non-mixer), jackpatch, patchage (graphical jack patchbay), an audio timeline (non-timeline), and renoise. renoise and hydrogen are the only two utilities that i need to fiddle with, to open and save their respective sessions

nsm isn’t an arbitrary choice from among many competing session managers. firstly, there aren’t that many to choose from (otherwise LASH and Jack-Session). secondly, nsm elegantly achieves what previous session management tools were supposed to, hence it can be considered the current standard for linux audio session management. there is already a choice of excellent multi-tracks, mixers, patchbays, sequencers, plugin hosts, and other tools with full nsm support (see an incomplete list, here: )