Clean RFC 2119 language

- Replaced RFC 2119 languages in non-normative sections.
comment-29

- s/The set of connected peers/The set of directly connected
  peers/
comment-31

- Rewrote the definition.
- Extended the example to include application IDs.
comment-40

- Put the word routing between quotes, to emphasis that there is no
  routing at all.
comment-47

- Added a definition for a RELOAD user.
comment-49

- Fix as suggested.
comment-50

- Fix as suggested.
- Added spacing between eleemnts of the list.
comment-51

- Fix as suggested.
comment-56

- s/High Performance Routing/Optimized Routing/
comment-57

- Fix as suggested.
comment-59

- Added "transient".
comment-60

- Add "(storage indices, not encryption keys)"
comment-61

- Added reference to wikipedia.
comment-62

- Added definition for Kind-ID.
comment-63

- New text: A value of fixed but configurable length that
  uniquely identifies...
comment-65

- Paragraph deleted.
comment-72

- Fix as suggested.
comment-73

- Fix as suggested.

[will need rebase when 6125 is used instead of 2818]
gen-art-12

- Split 5th paragraph of section 6.1.2 to separate normative text from
  example.
- Removed commented text.
- Rewrote 9th paragraph without the example.
- Removed the "provided by..." sentence that does not make sense.
gen-art-13+14+15+17+18

- "a node constructs" -> "a node MUST construct".
- "resulting message will use the normal overlay routing" ->
  "resulting message MUST use the normal overlay routing".
- "The node can also" -> "The node MAY also".
- "Because messages> may" -> "Because messages can".
- "the request is retransmitted" -> "the request MUST be
  retransmitted".

Closes #149
Closes #150
Closes #151
Closes #153
Closes #154