Changed title for page and restructured with simple overview content for each area with hide/show links to provide the more detailed content.
Restructured content with simple overview write-ups and hide/show links to the more detailed content and examples.
Merge branch 'composition' of https://github.com/STIXProject/stixproject.github.io into composition
Modified "Selecting level of detail for observable composition" section with short intro, simplified first column content and added an example column
Minor tweaks and fixes
Merge branch 'composition' of https://github.com/STIXProject/stixproject.github.io into composition