Documentation checks

[CBenghi]

• We should add a note to explain the limited LOIN support to the documentation for 1.0, see Construction phase/LOI related IDS Check #232

[atomczak]

Made the documentation of IDS Purpose and Milestone aligned with Purpose (5.2) and Milestone (5.3) of LOIN standard. Our documentation does not mention the standard to keep IDS universal. I think an explanation of how IDS can support LOIN in practice could be an external article instead.