web experience improvements

• bug fixes
• performance improvements

detailed changes:

Based on visual inspection of page views since the previous release, and based on the increased server load during S230518h, the following changes are implemented in this release:

• tweak robots.txt to allow scraping of public pages (increases search engine visibility of LVK events). Note: the crawl-time is still set to 1024ms per page, and server load due to robot processes on the web is small.
• take out vestigial javascript on superevent and event pages to increase page view performance.
• fix css that resulted in a broken "Public Alerts" button when other bootstrap buttons were visible on the page (like the alerts signup and pipeline management pages)
• fix pipeline-preferred event table bug that incorrectly showed only preferred-preferred event pastro and embright info.
• file list and query improvements
• improved caching of public files accessed via (/apiweb/)
• tweak apache KeepAliveTimeout to improve server stability when under load (this is still under testing, but is encouraging so far)
• Add ENABLE_UNAUTHENTICATED_ACCESS deployment variable to optionally enable/disable public access without rebuilding new containers
• fix public alert page to capture public detection candidates in between O4/O3 (S230518h)