Added lint support via command line

Hi,

here is a pull request for maven-android-plugin that adds [lint](http://tools.android.com/tips/lint) support to maven builds.

It supports almost all command line options and can be configured in the standard mojo way : 

```xml
 <plugin>
                                <extensions>true</extensions>
                                <groupId>com.jayway.maven.plugins.android.generation2</groupId>
                                <artifactId>android-maven-plugin</artifactId>
                                <version>${android-maven-plugin.version}</version>
                                <executions>
                                       <execution>
                                       <id>lint</id>
                                       <goals>
                                         <goal>lint</goal>
                                       </goals>
                                       <phase>install</phase>
                                       </execution>
                                </executions>

                                <configuration>
                                        <androidManifestFile>${project.basedir}/AndroidManifest.xml</androidManifestFile>
                                        <assetsDirectory>${project.basedir}/assets</assetsDirectory>
                                        <resourceDirectory>${project.basedir}/res</resourceDirectory>
                                        <nativeLibrariesDirectory>${project.basedir}/src/main/native</nativeLibrariesDirectory>
                                        <sdk>
                                                <platform>7</platform>
                                        </sdk>
                                        <undeployBeforeDeploy>true</undeployBeforeDeploy>
                                        <lint>
                                                <werror>true</werror>
                                                <failOnError>true</failOnError>
                                                <skip>false</skip>
                                                <xml>${project.basedir}/lint-result.xml</xml>
                                        </lint>
                                </configuration>
                        </plugin>

```

I am really sorry as I couldn't manage to configure eclipse to fit your coding convention. I disabled checkstyle in my pom.xml (but didn't commit it). The pull request works but you will have to re-format the code to match the plugin coding convention. Again, really sorry for that, I am a newbie with checkstyle and couldn't make it working on the project. 

Hope this helps. Personnaly, it will allow to move forward to a sonar lint plugin for android.