Filter raw values should not be escaped

[jsumners]

Every case of escapeFilterValue in the following should be removed:

filter/lib/string-parsing/parse-expression.js

Line 55 in 7876f8d

value: escapeFilterValue(remainder)

The escapeFilterValue should only be used in the toString method of each filter. The raw value is the one sent to remote LDAP servers, and the specs dictate that the escape character should not be included. For example í should be sent as c3ad, not as \c3\ad.

This is the culprit behind ldapjs/node-ldapjs#860.