yotam: improvements and bug fixes to search feature, changes in is_comment logic

- search now addresses tags, split keyword search by comma, reorganize clause joining logic (INCOMPLETE)
- refactoring the process of joining different clauses together to be cleaner, and handle empty queries
- some in-code documentation and printing to server console.
- page title of search result is set with a special context parameter  search_title (still hardcoded)
- added 'commented on this' to is_comment string search
-some minor indentation changes
yotam: improvements to search feature, round 2

- keywords are passed and handled as quoted strings
- and/or logic between tags and keywords queries are now selected as input by user.
- minor cleanup to search GET request built by searchgui.js