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

PR Number

11,076

Customer

None

Course

None

OSCM Assignee

None

Github Latest Action

None

Github Latest Action by edX

None

Github PR Last Updated At

None

Github PR Last Updated By

None

Impacted Users (OSPR)

None

Impacted Environments (OSPR)

None

Feature Control (OSPR)

None

Story Points

2

Sprint

None

Priority

Unset
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