rmb deep documentation in mdbook

[despiegk]

• describe messages of rmb
• how does it work
• how to use from V (is V compatible with latest version)
• how is security done
• how is redundancy

make sure mdbook gets deployed as described on spiderlib

[xmonader]

first two parts are addressed in https://www2.manual.grid.tf/internals/internals.html

more elaboration need to happen on the security part, and redundancy needs to be resolved first