Animal Sniffer Plugin applied for Java compatibility test

[jaemin-shin]

• Now the plugin tests whether APIs used for pinpoint are compatible for java 1.6.
• Two files are modified: pom.xml, web/pom.xml
• This test automatically runs during project build. (ex command/ mvn install -Dmaven.test.skip=true)

**pinpoint-web is tested if it is compatible with java 1.7
**sun libraries are ignored at the test.

naver/kaist-oss-course#65

[Xylus]

@999fg
Looks good!
One possible suggestion would be to pull sniffer artifactId out as a maven property.
This way, web's pom.xml could simply overwrite this property to java17 instead of redefining the whole plugin. (Similar to how the maven-compiler-plugin is using jdk.version to configure source and target levels)

Automatically setting sniffer's artifactId based on jdk.version would be even better, but I'm not sure if this can be done easily.

I'd love like to hear what you think, please let me know.
Thanks!

[jaemin-shin]

@Xylus

Thanks for the comment!
I totally agree with your suggestion, which is more good way of coding and compatible in further development.
When I sent this PR few hours ago, I personally did not like two lines of log appearing when pom-web is being compiled (possibly due to re-defined plugin application in two pom.xml file). Following your suggestions solved this problem.
Anyway, I updated the commit as your suggestion.
Thanks!