Add generic install instruction for linux

The current install instructions pretty much leaves anyone not using a small handful of linux distros in the dark, you either endlessly build and respond to build failures, sift through the distro specific scripts hunting down dependencies your distro lacks, or dig through the source files to find dependencies. There should be instructions listing all dependencies which are not standard on most distros.

Start by locating the Linux installation documentation, distro-specific scripts, and source files that reveal dependency requirements. Document the dependencies that are not standard on most Linux distributions, with enough coverage for users outside the currently supported distro set; the generic instructions should let them install without digging through scripts or source.