Fix images in single and multi select problems in libraries. Found following issues and fixed them:
* Images were not being rendered in any of the fields in these problems.
* Base url was not being set which is used by tinymce to load images with relative path.
* Answer fields were set to inline mode which does not initialize images or base paths
* If same image twice is used twice in a problem, the logic of replacing `static/image.jpg` with `/static/image.jpg` would replace the first occurrence twice resulting in `//static/image.jpg`, breaking both the links.
* On initialization of answer fields, the absolute static asset urls were being replaced by relative urls causing the editor being set as dirty without user changes.
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