Send daily statistics to admin

[php-coder]

As an administrator of the site I want to know the following information (with links to appropriate pages):

• How much countries have been added?
• How much categories have been added?
• How much series have been added?
• How much users have been registered?
• How much users have been activated their accounts?
• Home much suspicious events have occurred?

[php-coder]

The step by step guide for you, because this feature involves changes in many places:

• CronService{,Impl}: add method that will send this statistic every day (it should be invoked before purgeUsersActivations() to have information about registered but not activated accounts, so, probably we will change the @Scheduled of this method too to use cron expressions)
• MailService{,Impl}: add method for sending e-mail
• MailTemplates{,_ru}.properties: add text of subject and body of the e-mails
• CountryService{,Impl} (+ DAO): add method for counting how much countries have been added
• CategoryService{,Impl} (+ DAO): add method for counting how much categories have been added
• SeriesService{,Impl} (+ DAO): add method for counting how much series have been added
• UsersActivationService{,Impl} (+ DAO): add method for counting how much registration requests have been created
• UserService{,Impl} (+ DAO): add method for counting how much users have been registered (activated their accounts)
• SuspiciousActivityService{,Impl} (+ DAO): add method for counting how much suspicious events have occurred

[php-coder]

CronService{,Impl}: add method that will send this statistic every day (it should be invoked before purgeUsersActivations() to have information about registered but not activated accounts, so, probably we will change the @Scheduled of this method too to use cron expressions)

I've implemented it in 3b58025 commit.

[php-coder]

Also we should include info about changes in the series.