New changes and bug fixes

[a-mabe]

• Fixed Firefox issue
• Changed histogram page layout
• Added stats page functionality for date range
• Changed date range input format
• Removed unnecessary cache file creation for histogram page
• Refactored back end
• Fixed histogram page not fully loading

[ibnesayeed]

Let me know when it is ready to be merged.

[a-mabe]

It is tested and ready to be merged, thanks!