large amount of fixes

large amount of fixes related to performance and usage simplification
- fully rewrite server-side preprocessor file
- optimize and simplify client-side code
- multiple entries can now be queried without having to open the multi
tab (the form for single queries now accepts multiple values separated
by commas)
- the diff now accepts queries whose values are given as parameters in
the url
- the multi tab can now be emptied
- buttons and some other types of input fields now have a new design
- close buttons are now red on tabs