Add more documentation to the wiki and code

We are missing a lot of documentation on how things work internally. For instance, I have no clue how argobots tasklets are used in the daemon and how they relate to the threads in the I/O pool. I suggest that we make a collective effort to write a general technical documentation (doesn't need to go into code level details) so that any future developers starting from scratch have something to get them up to speed fast. We probably already have lots of details documented in slides and papers, it would be a matter of structuring the information better.

PS: Also pictures, lots of pictures :)

General tasks:

• Add documentation to the public wiki (TODO subtasks)

Client tasks:

• Complete function documentation for Doxygen
• Check existing inline code comments for correctness
• Add general documentation for the purpose of each header/source file

Daemon tasks:

• Complete function documentation for Doxygen
• Check existing inline code comments for correctness
• Add general documentation for the purpose of each header/source file