And adds TapeServer.pdf to repo

Renamed CTA/tapeserver/castor to CTA/tapeserver/castor_checkout in preparation for the moving the sub-directory CTA/tapeserver/castor/castor up the directory tree

Added a small section on how-to compile catsor on SLC and possible issues which can be faced while doing so

Fixed the read session memory management layout as the file size if not know before hand
(and not really needed, as we read files and consume free blocks in sequence.
Extended the description of the file support classes.
Fixed minor compilation issue.

Fixed inheritance from std::exception (const correctness of what()). This required declaring m_what mutable.
Created a multithreaded unit test.
Created an automatic exception thrower for unhandled errors.
Ported from previous proof of concept the threading primitves and made them production level (with error checking).
Added unit tests for threading primitives.

Checking in PDF as the graphs use packages currently unavailable in SLC5.
Updated cmake/rpm to use the pre-packaged pdf.

The doc compiles with a recent TeXlive, but probably needs importation of packages to compile in SLC5/6...