add times logged in the users list

(cherry picked from commit d23844eaa03e417bb36e770c068e98bd04312279)
add user count in users' list

(cherry picked from commit 338a6c73f0475c2798e6d431d1bc32b0a81aa03c)
add counter of how many times a user has logged in

(cherry picked from commit 3b182a70a10439d875f688cecdfc43457abdf63d)

Conflicts:
	app/controllers/application_controller.rb
	db/schema.rb
refactor: extract query for similar alerts to model from views

this is the first step to implement issue#15