minor doc tweaks
minor adjustments to system configuration

includes,
* link to memory settings configuration
* removal of OpenGL clients (coming real soon)
explain more about the binary repository
reorder lists of operating systems to promote Linux

suggested by @manics
reword sentence to remove active voice

suggested by @bpindelski
adjust suggestions / recommendations for security support

also reformat file markup
suggested by @rleigh-dundee
remove ambiguous adjective
Merge pull request #951 from mtbc/server-config

improve and update server configuration documentation (rebased from develop)