Supports V1 and V3 Mailjet's users

Supports V1 and V3 Mailjet's users, the version of the plugin is changed
to 3.1.0 because this change is major
Revert "Supports V1 and V3 Mailjet's users"

This reverts commit 180ed0e3ad37ee462916f8144e02bf052cfe9e5c.
Set IsActive to be TRUE for newly generated TOKEN

Every time when we generate a new TOKEN we set the parameter IsActive to
be TRUE (Related to redmine issue #1488)
Merging branches

Merging branch "pavel" (version: 3.1.0) with master's branch (version:
3.0.3).
Merge remote-tracking branch 'origin/development'
Merge pull request #6 from mailjet/development

Merge the development and master branches
Merge pull request #7 from mailjet/development

Merge development with master
Merge remote-tracking branch 'origin/development'
Prevent plugin from hiding other plugin's page
Prevent plugin from hiding other plugin's page #10

Prevent plugin from hiding other plugin's page #10