Tidying editor & web sections
Adding image & sorting heading hierarchy
Final nitpicks from Mark
And the ones I missed!
Updating Python version required
VistorPatter to VistorPattern
Fixing demo server page
Merge pull request #254 from hflynn/dev_fix3

Developer docs tidy 3
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken: PR 245 (Add note about Java UTF-8 source in Insight.)
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken: PR 255 (Redo user doc front page & replace old tutorials with training materials)