Add support for `+ !` operator in meta

[ashleyse2016]

Currently OA does not allow for the operator + ! in the meta part.

Eg:

meta OA_LOCAL_EXAMPLE __OA_LOCAL_EXAMPLE_02 && __OA_LOCAL_EXAMPLE_03 && (( __OA_LOCAL_EXAMPLE_01  + ! __OA_LOCAL_EXAMPLE_08 )

Changing to + ~ works, as would && ! however + ! should also be allowed.

[georges96]

Complex rules using this rule are failing therefore the daemon fails to start. An example of such rule is
body __LOCAL_TEST1 /\btest1\b/ body __LOCAL_TEST2 /\btest2\b/ body __LOCAL_TEST3 /\btest3\b/ meta LOCAL_MULTIPLE_TESTS (((0.8 * __LOCAL_TEST1) + !(0.5 * __LOCAL_TEST2)) > 1) score LOCAL_MULTIPLE_TESTS 0.1
The rule works fine if i use + ~ instead of + !. My guess here is that the round brackets are affecting the regex or something.

[georges96]

However the operator + ! seems to work for simple rules.