[FEATURE] Enable Mobile Navigation to bottom
This pull-request contains new constant - themes.configuration.menu.main.mobileNavigationToBottom whicj calls "Enable Mobile Navigation to bottom". By default it equal to 0.
The constant makes mobile navigation be placed to the bottom of the screen on mobile and tablet (max-width: @screen-sm-max).
As we need additional space at the bottom of the page - I choose to add an additional class to the footer, as footer is used in all our layouts, accept Empty one.
UPD: Move the mobile button to the bottom of the page

When we apply Header -> themes.configuration.elem.status.showHeaderTop')}==0" Main Menu -> themes.configuration.menu.main.enableLangMenuInNavigation 1 and user click on language flag -> dropdown is cropped.
Also if apply Mobile Navigation Toggle Btn = right, it doesn't change the position of items and it dropdown is cropped too.