Added new commands to Bstgen
Description
Added new ways to make projects with bstgen and updated the cli etc.
Bstgen now has:
- more flexiblity when making simple projects
- ability to make
fan
like projects
This MR should close https://gitlab.com/BuildStream/benchmarks/issues/21 as phil has show that the fan projects have similar performance profiles to reinvent projects
Edited by Javier Jardón