[search] Redesign search features

• rearrange layout (template & css) for sort filters on start page
• add global search and filter options on start page
• add search feature in navigation
• rearrange layout (template & css) on search results page

To be ported from Guides:

• https://gitlab.com/HistoryAtState/guides/commit/d14c9001ab8688e60015f2dd39e9140b01562e1b
• Most commits from https://gitlab.com/HistoryAtState/guides/merge_requests/18/commits

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Related feature requests #76 , #67 (closed)