Changed ../server/plugins/ location

Instead of a /server/ folder inside the project's own directory, i move it
outside the project folder so that it can be shared between multiple
projects.

OLD: ./server/plugins/BombArena.jar
NEW: ../server/plugins/BombArena.jar

plugin.yml: correct url typo.

VersionFormat.java: added ability to retrieve version integers consisting
of X number of digits (instead of 6 digits).

BattleArena is still done with a 6 digit comparison. However, this opens
up the possibility to use more or less digits for other plugins.

package-info.java: These files contain the the Javadoc comments for each
package.