Reworked command IDs to avoid collisions; see full commit message.

Cmd::IDFields:
	added flag_host and assign().

Cmd::Stage:
	added ID properties; modified m_id to alias the canonical ID.

System::Context:
	made initiate() assign ID fields immediately;
	simplified push_output();
	reworked execute_input() to avoid ID collision (woo!);
	changed some doc wording, prevented adjacent @note joining.