Deleted HoloManager.java

The purpose of the HoloManager was to keep track of Holograms and pass out
IDs, and use those IDs later to delete Holograms.

Each implementation of the HologramInterface now does the work of passing
out IDs because (for example), the parameter for addHologram() can be
com.gmail.filoghost.holograms.api.Hologram
or
com.dsh105.holoapi.api.Hologram

So at first, it might seem like duplicate code... But really, it's more
like overloaded methods.
Added debugging lines

for HoloAPI during configuration loading.
HologramInterface implementations

There are 3 implementations:
HolographicDisplay.java
HolographicAPI.java
HologramsOff.java

Tested and working. Only minor bugs.

HoloAPI has a minor bug with VirtualPlayers.

HolographicDisplays has a rare bug that occassionally displays holograms
underground (for items thrown really high + far). But I think I can
compensate for this behavior in the calling code.