minor corrections

- Explained the sblock question
- There are no 'paths'. There is no 'flow'. There are only links!
- Moved the explanation of what the blocks do to a more logical place.
As discussed many, many months ago in older discussion, this is completely uncorrect.
Microblx should be used anywere, ubx is related to the software.
That is, you find ubx in the code or repositories names, during developing. but it is never used in the documentation if not related to a code detail.