Backport search improvements, remove SEARCH_LIMIT

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/dynamic_search/literals.py

@@ -0,0 +1,12 @@
+from __future__ import unicode_literals
+
+QUERY_OPERATION_AND = 1
+QUERY_OPERATION_OR = 2
+
+TERM_OPERATION_AND = 'AND'
+TERM_OPERATION_OR = 'OR'
+TERM_OPERATIONS = [TERM_OPERATION_AND, TERM_OPERATION_OR]
+
+TERM_QUOTES = ['"', '\'']
+TERM_NEGATION_CHARACTER = '-'
+TERM_SPACE_CHARACTER = ' '