book: split srm chapter into srm, srmmanager, spacemanager

Motivation:

The `srm` chapter contains a lot of information unrelated to the srm door,
which both makes filtering out the srm door information difficult, and
complicates finding the srmmanager/spece management snippets when one if
looking for them.

Furthermore, a lot of the srm/srmmanager information is deprecated and
references properties that have become obsolete years ago.

Modification:

Splits the srm chapter into three new chapters: srm, srmmanager, spacemanager.
These chapters still need reviewing and probably more information down the line, though.
Removes mention of many obsolete properties.

Result:

Less deprecated book content.
Hopefully it will also be easier to find information on both srmmanager and
spacemanager.

Target: master
Requires-notes: no
Requires-book: no
Patch: https://rb.dcache.org/r/14123/
Acked-by: Tigran Mkrtchyan