Remove empty/duplicate/unpublished content.
Link to replacement attributes for obsolete report_data_select

Redmine#5298
First unpublished version of upgrade guide to 3.6.
Fix sorting in component list.
Link to cfmigrate binary.
Various formatting fixes.
Macros won't work within lists, breaks numbering.
Comment out platform list for master builds of documentation.
Publish upgrade to 3.6 documentation.
Leave the additional platform section in so that links resolve
s/3.6.0/3.6 where appropriate.
Quote 3.6 to make Jekyll happy.
Remove old upgrade guide
Fix linking in indented paragraph
Upgrade documentation covers source versions 3.x
clean up upgrade docs