Merge pull request #607 from mmklee/dox

More / better Doxygen descriptions + cleanup & update
Added and referenced the old Singular C/C++ Coding Style guide

NOTE: the style guide (v1.0, May 27 2010) was originally contributed by Frank Seelisch
Doxygen should also look for markdown files (*.md) as well as C_CPP_StyleGuide.md
Renamed README into README.md + include it into doxygen manual
Use README.md as mainpage for Doxygen manual

NOTE: former mainpage is now main_page
fix: debug version must have no output if everything is okay!
chg: fixed wrong warning, better comment: try_omit_comp
Albert Heinle: new ncfactor.lib
fix: assign def,def=matrix
cleanup interpreter
fix: spoly(poly,vector) is legal: res in q-ring case
fix: parameters for numeric: visible sizei(>=6), additional size(>=0)
doc: cfSubringGCD
doc: cfSubringGcd
Fixed the deps. between doxy pages
fix: typo
Added an unit test to polys/
Starting to document directores with Doxygen
Fixed BS (.libs)
Simplified syzextra testing