Add message showing the number of search results (#1524)

* Added message showing the number of search results

Modified _search_journal() to return a bool based upon whether
any filter args were passed to the program.

Added _print_entries_found_count() which prints a message
based upon the number of entries found and prints warnings
if the user was trying to edit or delete.

* Add tests for search results msgs

jrnl/messages/MsgText.py

@@ -224,6 +224,10 @@ class MsgText(Enum):
         No entries to modify, because the search returned no results
         """
 
+    NoEntriesFound = "no entries found"
+    EntryFoundCountSingular = "{num} entry found"
+    EntryFoundCountPlural = "{num} entries found"
+
     # --- Formats --- #
     HeadingsPastH6 = """
         Headings increased past H6 on export - {date} {title}