Rewrite index search and text search(and fix #913 and #905)

Have tested the index search in its coverage, and validity of the urls.Works well.

Know issues and next step:
1 Do not works for some symbols, big theta for example (though I do not think user can easily input and search for them as well)
2 Do not treat what is designed to be latex, roman, italic properly, now treat them as normal text.
3 No "see also in index, might be a good next step to add them.
4 Find clever and more robust way to test for the correctness of the url generated. (Other than manual tracing)
5 No automate test done on text search yet.

Also manually check for issue mentioned in #913 and #905 after rewriting. Unsurprisingly, they are all fixed.

I still kept the old "generateSearchData" as the frontend have not been updates yet, and the current frontend depends on it.