Generalised row strategy to base strategy
Added arbitrary order strategy
refs #850
Fixed arbitrary order strategy declaration
Changed scanning-order type to string
refs #850
Changed strategy in main group in symboler
refs #850
Added naming pager's page (based on its id)
refs #850
Added page to scanning order
refs #850
Merge branch 'master' into symboler-short-circuit-2

Conflicts:
	pisak/pager.py
	pisak/scanning.py

refs #858