Fix #37 Small refinements to the dataset level page

[harikiranrommala]

Here are some small fixes

• the database link to the right of the Home icon on every Dataset page is not working, for example
  
• the text-valued JSON keys in the JSON view should have the following css setting to limit the height and use ... to overflow.

    overflow: clip;
    text-overflow: ellipsis;
    display: -webkit-box;
    -webkit-line-clamp: 4;

• in my jsonview.traverse() function, I also scan over all string-valued fields, and encloses the values with <code class="puretext">...</code>, and set code.puretext css with white-space: pre-wrap; in order to properly show the newlines in the strings
• the script to download all files button is not working, for example https://zodiac.coe.neu.edu/dev/dev_hari/databases/defenderfer-2019/S1001_run01
• the download dataset button also report incorrect file size, again, you can test it using the above link