Ignore whitespace around rule

[kumavale]

Fixes #571

Allow rules in 'rules.conf' to start and end with spaces. It also allowed lines with only spaces.

$ cat -A rules.conf
allow $
 $

I would like to allow these characters because they are invisible, but I would like to hear your opinion about lines starting with spaces.

$ cat -A rules.conf
 allow$

[Cropi]

Hello, Wouldn't it be better if the rule struct had an optional comment at the beginning of the rule? Similar to how the optional comment at the end is being handled? In that case the rule_gramar would not require changes.