Allow for custom lib and conf file placement.

Leveraging the great custom file placement feature already built in and continuing to rely on ant for placement, these changes allows a developer to place 3rd party or private jar files that is used in code being overridden alongside the rest of the jar files in lib. Similarly, related changes in conf will also be placed appropriately during the build. An example scenario might be having a custom auth provider, which can't be placed inside a plugin, and requires 3rd party jars.

Discussion: https://community.igniterealtime.org/message/241603#241603

Note: had to re-create the pull request after switching away from master to do pulls. Previous pull request (now closed) with comments from deleolajide here: https://github.com/igniterealtime/Openfire/pull/60