Rename comments table to activity
DDL and code updates

- Update activity table schema to work with activity log type data
- Add records for issue being opened to the log
- Record comments to activity table
Add the activity log to the issue view
Add close records
Merge branch 'master' into activity_log
Update the sample data for the new schema
Add activity logging to the hooks
Merge branch 'master' into activity_log
Update updateComments method to new schema
Fix project selector doesn't submit the form on change (where it should)
Fix extra fields textfield values can not be saved
Fix extra fields "general failure" (Ref #69)
Fix extra fields "general failure" admin part (Ref #69)
Merge remote-tracking branch 'origin/master'

Conflicts:
	components/com_tracker/view/add/html.php
	components/com_tracker/view/edit/html.php
	components/com_tracker/view/edit/tmpl/fields.php
Don't store empty fields
Fix add form redirect when server side validation fails
Add username to Modified so users can see who last made a comment or edited a ticket without having to open the ticket up.
Change the category to be an extra field [DB CHANGE]
Add project handling (Fix #31) (Fix #38) [DB UPDATE]
Update sample data