Changes to tabs

Here are changes that would make me happy with regards to the tab functionality/bar:

- Allow for the deactivation of tab functionality for those who do not want to either read or compose mail in a tab

- that tab bar being there doesn't bother me and offers a nice shaded separation, the links to the right are nice and simple but: why does clicking on one of them remove that link to open a tab instead? Isn't that redundant and wouldn't it be better to just highlight that link so we know that we are looking at the attachments for example?

- Allow for the option to disable the tabs as they are used now, keep the links on the right side and add an extra link to the left of them that could be for example "Messages" (when the user has elected to not use tabs). Using those links, which can have an active state, one can switch between message view, attachments view etc...(mostly *like* tabs)