Render lms main navigation (tabs) with template

Description

The reason for this pull requests is the conversation with @singingwolfboy in Slack:
https://openedx.slack.com/archives/theming/p1449519743000017

Someone wants to rename the “Courseware” tab in the LMS navigation and for now there is no ability to make it easy (only one way to do it is to override the entire template).

With this little improvement every tab could be redefined (for example in microsite theme) with adding specific template (by default courseware/tab_default.html will be taken):
```
courseware/tab_courseware.html
courseware/tab_info.html
courseware/tab_discussion.html
courseware/tab_wiki.html
courseware/tab_progress.html
courseware/tab_instructor.html
```

Status

Assignee

Matthew Drayer

Reporter

Edx Admin [Administrator]

Contributor Name

Dmitry Viskov

Repo

edx/edx-platform

Customer

None

Epic Link

None

OSCM Assignee

None

Platform Map Area (Levels 1 & 2)

None

Platform Map Area (Levels 3 & 4)

None

Story Points

2

Priority

Unset
Configure