Finish adding 'Type' column to tables

See line comments for suggested discussion points for this commit. 
Add explanation of agent account

The wording of this may need to be discussed.
Explained phrase 'opaque account'

Also added some rationale to when this might be used. 
Reword first sentence of verb section

Removed a lot of words that aren't really needed. 
Added an extra sentence.
Changed paragraph spacing
merged two very similar paragraphs

Also replaced "Tin Can" with "Experience" for consistency (though I will personally continue to refer to the 'Tin Can API'). 
various minor amends
minor chnages to context and timestamp
Merge pull request #4 from garemoko/workingCopy

merge working copy to garemoko master
moved context activities to its own section

Further explanation of 'parent', 'grouping' and 'other' to be added. 
changes to context activities

these will need some discussion
changed URI to URL

Because the requirement to make a human-readable description at 
a URI only makes sense for URIs which are URLs. 
Changed format of endpoint examples
various minor amends
Merge pull request #5 from garemoko/workingCopy

Merging changes to 'Working copy' into 'master' ahead of tomorrow's meeting
replaced "order of the statement"
changes as discussed https://github.com/adlnet/xAPI-Spec/pull/10

Also added 'Epic' as my Organization, but that should be uncontroversial.
Merge pull request #6 from garemoko/workingCopy

merge Working copy
Merge pull request #10 from garemoko/master

Various minor changes