Bug 22228: Escape lone colons and make sure term is balanced

Bug 22228: Escape lone colons and make sure term is balanced

Escapes unquoted colons that have whitespace on either side. Removed unbalanced quotes.

Test plan:

1. Make sure the test case described in the bug works
2. Make sure tests pass:
  prove t/Koha/SearchEngine/Elasticsearch/QueryBuilder.t

Signed-off-by: Björn Nylén <bjorn.nylen(at)ub.lu.se>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>