Fix accidental type conversion in sluggable behavior.

This generated code:

    $slugNum = substr($object->getAccountId(), strlen($slug) + 1);
    if (0 == $slugNum[0]) {
        $slugNum[0] = 1;
    }

    return $slug2 . ($slugNum + 1);

will turn `$slugNum` into an array if substr returns false. By checking
with `===` against `'0'`, this is avoided.
fixed a getter function without '$con'
Added type-hinting on doAdd crossFK generated functions
Merge pull request #765 from rvitaliy/connection-fix

fixed a getter function without '$con'
Merge pull request #766 from rvitaliy/doAdd-fix

Added type-hinting on doAdd crossFK generated functions
Merge pull request #707 from gunnarlium/bugfix-sluggable-fails-when-string-is-empty

Fix accidental type conversion in sluggable behavior.
Fix CS
Prepare 1.7.0 release
Bump version to 1.7.1-dev
Allow gh-pages to be tested