0024722: Move functionality of WOK command wgendoc to OCCT tool gendoc

0024722: Move functionality of WOK command wgendoc to OCCT tool gendoc

Command gendoc improved to:
- generate Reference Manual documentation (OCCT classes reference) with option -refman; option -overview can be used for generation of overview documentation;
- generate PDF documents for all User Guides automatically (for files listed in FILES_PDF.txt);
- check availability of third-party tools (Doxygen, Inkscape etc.) and properly report warnings and errors.
- use templates of configuration files for third-party tools instead of their generation. These template files are located in dox/resources folder

Tcl scripts are moved from dox folder to adm.
Doxygen warnings are eliminated.
Moved all auxilary functions to occaux.tcl.
Fixed Reference manual generation on *nix platform.
Fixed PDF generation on *nix platforms.