add login btn in main site header
wip add logout
Merge branch 'develop' of https://github.com/VarnaLab/varnalab.org into develop

Conflicts:
	context/UI/styles/less/varnalab-header.less
fix logout and spec
added login/logout
Merge pull request #54 from VarnaLab/logout

Login and logout buttons added to layouts of the site and admin