bugzillaId-604: Module load path documentation issues ...

This is imported from bugzilla item http://bugs.mariadb.com/show_bug.cgi?id=604

Description Hartmut Holzgraefe 2014-11-01 11:50:58 UTC

• The module load path is only documented in the "Protocol Modules" subsection
  although it applies to all module types (this is the first module type
  described in the "Modules" section so it's unlikely to be overread, but still
  it's in the wrong place IMHO)

• the path given in "Protocol Modules" is wrong, it says

These modules reside in the directory $MAXSCALE_HOME/module, [...]

while it is actually .../modules (ending with 's'), not .../module

• the actual load path in server/core/load_utils.c is:

1) look for module .so file in the current directory
2) if that fails: look for it in $MAXSCALE_HOME/module

Suggested fixes:

• remove loading from current working dir completey (cough security cough)

• fix path in documentation

• move load path description from "Protocol Modules" section to
  a more general one, e.g. a general "Introduction" part at the
  start of the "Modules" section