Search improvement
    
    Summary:
    Exact search checkbox removed, search now works as follows:
    - you can use `*` or `%` as wildcard
    - with no wildcard, substring search is performed (same as `*item*`)
    - wildcard can be in the middle of search query (e.g. `python*fc22`)
    
    Test Plan: `$ python runapp.py` nad try it
    
    Reviewers: kparal, jskladan
    
    Subscribers: tflink
    
    Differential Revision: https://phab.qadevel.cloud.fedoraproject.org/D416