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 extra fields validation (Ref #69)
Add support for issue relations (Ref #76) [DB UPDATE]
Add a base project class
Mostly to add type hinting and code assist.
Add support for a link to a GitHub commit where an issue has been closed [DB UPDATE]
Add missing table for relation types [DB UPDATE]
Merge remote-tracking branch 'origin/master' into activity_log

Conflicts:
	cli/retrievecomments.php
	cli/retrieveissues.php
	components/com_tracker/view/issue/html.php
	components/com_tracker/view/issue/tmpl/default.php
	libraries/tracker/table/issue.php
	sql/sampledata.sql
Fix too much merged
Merge pull request #66 from JTracker/activity_log

Activity log
Fix wrong table name [DB UPDATE]
Fix missing project_id in activity stream in CLI importer
Make the CLI scripts more db agnostic (tested with SQLite)
Plus some minor tweaks