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
Installation: Specify what to do for N/A in package lists
Installation: homebrew mplayer provides mencoder
installation: change 'is largely' to 'are mostly'
installation: Remove double spaces and reflow
Merge pull request #951 from mtbc/server-config

improve and update server configuration documentation (rebased from develop)
Merge pull request #956 from rleigh-dundee/install-ice-dev50

Installation: Specify what to do for N/A in package lists (dev_5_0)