Allow multiple banned-import-groups within a single enforcer rule

[skuzzle]

This would allow influences of rules to other rules. My favorite:

• A source file is only subject to a single group
• The group to which a source file is subject is chosen by the longest basePackage pattern which matches the source file

...
<bannedImportGroups>
    <bannedImportGroup>
        <basePackage>com.foo.**</basePackage>
        <allowedImports>...</allowedImports>
    </bannedImportGroup>
    <bannedImportGroup>
        <basePackage>com.foo.bar.**</basePackage>
        <allowedImports>...</allowedImports>
    </bannedImportGroup>
</bannedImportGroups>
...

In this sample, source files from com.foo.bar would only be subject to the rules within the second group.

Another approach could be that all groups are applied to a single source file and groups with a more specific basePackage can override rules from groups with less specific basePackage.

[skuzzle]

This will be implemented as follows:

1. Multiple banned import groups can be specified per EnforcerRule definition
2. When analyzing a source file, the group with the most specific base package pattern matching the source file's package will be chosen
3. Specifity of package pattern can roughly be described as follows 3.1. p1 is more specific than p2 if p2 contains more ** parts 3.2. p1 is more specific than p2 if p2 contains more * parts 3.3. If both patterns contain equal amount of ** and * parts, the pattern with the most specific last part is more specific than the other

[skuzzle]

Released as 0.13.0