Add background daemon

[poelzi]

We should add an background to which we can delegate work. This daemon should start n subprocesses to which he delegates his work. n is the number of processors in the machine, or user defined.

All pida instances should connect to the same daemon (prefered) but it should be possible to start an own one.

Each service/plugin can define how it's background process should run. Pida will be allowed to start start/stop subprocesses in the bg daemon, depending on its needs. The daemon will honor the parameters of the bg class/module.

• Run only in one process
• spawn n/unlimited worker threads in this process

Detect dead, locked bg daemons and restart if necessary.

Good candidates:

• filesystem abstraction layer. this will use gio and use gio's caching capabilities.
• use anyvc in this abstraction
• language service outliners, validators

[ali]

+1