BugzillaServer.java:
 - Cleaned up the imports; the exceptions are now under com.j2bugzilla.api.
 - Changed executeMethod() around to take in the parameters for calls - the method name, and the Map of the RPC parameters - and return the Map of the results. It's reasonable to have the new API implementation classes handle this stuff.
BugzillaServer:
    connectTo() methods no longer throw ConnectionExceptions. As discussed these will likely throw another kind of exception that inherits RuntimeException.

BugRepoImpl:
    Added bugFromMap(), which takes a Map (specifically, the one returned by an RPC call) and turns it into a Bug.
    Need to decide how to get the version -- my understanding is that this is a nuance to be handled by different implementations of the SPI.
    Need to figure out how to get the Product efficiently. Cannot tolerate making an RPC call every time. Likely, the ProductRepo should cache Products...