Technical debt

[dmytrostriletskyi]

The technical debt to solve:

• https://travis-ci.com/Remmeauth/block-producers-directory-back/builds/119434948#L968;
• https://travis-ci.com/Remmeauth/block-producers-directory-back/builds/119436437#L920;
• Find out if we can create generic database utils bash file.

Solved by #73:

• Add max_length to arguments in CreateBlockProducerForm validation form for block producer;
• With replace with without — https://github.com/Remmeauth/block-producers-directory-back/blob/develop/directory/user/tests/views/test_registration.py#L51;
• Create table for request parameters with token for refreshing and verification in Readme;
• Add username to URLs in change user password, update user profile and so on.