Added event, amount, pay_type(labeled as type in rails admin) to fee_plans table. Added custom validations for them.

== Rails admin note on pay_type ==

Actually I tried with type column at first and spend some time figuring why it's not working. Turned out that name can't be type, so I renamed it to pay_type. I'm really waiting for feedback on this one.
#552 fee plan
Show user's fee plan on profile page.
Added validations to fees
Displaying current fee plan on users profile.
Mockup for plan type dropdown in user sign_up form.
Better translation for dropdown.
Tom is right about this breaking rake install/seed, so just commented it.
Mockup for calculating fee demmurages at the every end-of-month with rufus scheduler 3.
added comment for cron statement
Added paid_fees column to accounts table to generate monthly fees invoice. - fix #426. As users take actions charges are recorded according to their Fee Plan - fix #552.
Display transaction fee on show page
Transactions should be calculated based on Exchange class, so we don't need paid_fees column. - fix #552
Fees based on trade credits should happen immediately. - fix #552
Braces' typos - weird that it was working in console
Divided 'Percentage' fee.event to 'Percentage(trade credits)' and 'Percentage(cash)'. New fees_invoice_for_month(month,year) method - fix #522, fix #426
Fixed typo.
Cash fees are aggregated and submitted to credit card processing in batches. Trade credits are payed immediately - fix for percentage(trade credits). - fix #552
Pay monthly fees at the end of month. - fix #552
Yearly fees - fix #552