init expression tree
implement search by pattern only with first expression
imrpove generating tree
imrpove expression tree
improve engine
implement booleanSearch
refactoring to object tree
code clean up
implement OR expression
add OR test to tag and url pattern
code clean up
don't calculate tree for same search text
merge commit with upstream dev
Merge pull request #74 from artemgrygor/master

Implement boolean search engine with AND-OR expression.