Updated help files with an updated introduction and document style from fthr, revised other existing documentation to conform to the new style and updated the build script to no longer build from markdown sources since we're now using HTML directly.
Updated the main style sheet to make the load / save filename input field a little less naff to look at, and easier to see in general.
Core: Added a "select all" (in the active graph) feature. Hotkey is CTRL/CMD+A.