Concerning the guidances (guidelines in particular), I simply had to
obtain a resourceSet from the file plugin.xmi, and not the .xmi file of my
lifecycle. Thus, the guidelines can return a name.
Concerning the problem about using my library in my Eclipse plugin, I
tried to add default plugins in "Open Run Dialog", and then remove the
useless ones, and add the missing ones, according to the error log. I was
finally able to start my plugin and use the library through it.